Acids and Bases I | Chemistry

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Also covered is a neutralization technique called titration."> <meta name="keywords" content="science, education, STEM, math, biology, chemistry, physics, earth science, online learning"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/chemistry/1/acids-and-bases-i/271" }, "name": "Acids and Bases I", "headline": "Acids and Bases I: Definitions, pH and neutralization", "author": { "@type": "Person", "name": "Robin Marks, M.A." }, "datePublished": "2020-07-30 15:26:15", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_271-23061209065116.jpeg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Whether maintaining water quality in a fish tank or suffering from acid indigestion, we encounter the effects of acid-base chemistry in many common situations. This module explores acids and bases and describes how our understanding of acid-base chemistry has been refined over the centuries. The module explains how the pH scale indicates acidity. A table of pH values demonstrates how familiar substances range from extremely acidic to extremely basic. Also covered is a neutralization technique called titration.", "keywords": "science, education, STEM, math, biology, chemistry, physics, earth science, online learning", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2020"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/chemistry/1/acids-and-bases-i/271"> <meta property="og:title" content="Acids and Bases I | Chemistry | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Whether maintaining water quality in a fish tank or suffering from acid indigestion, we encounter the effects of acid-base chemistry in many common situations. This module explores acids and bases and describes how our understanding of acid-base chemistry has been refined over the centuries. The module explains how the pH scale indicates acidity. A table of pH values demonstrates how familiar substances range from extremely acidic to extremely basic. 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href="/en/library/earth-science/6/ocean-currents/282">Ocean Currents</a></li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289">Water in the Atmosphere</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-i/202">History of Earth's Atmosphere I</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-ii/203">History of Earth's Atmosphere II</a></li> <li><a href="/en/library/earth-science/6/earths-atmosphere/107">Earth's Atmosphere</a></li> <li><a href="/en/library/earth-science/6/factors-that-control-earths-temperature/234">Factors that Control Earth's Temperature</a></li> <li><a href="/en/library/earth-science/6/circulation-in-the-atmosphere/255">Circulation in the Atmosphere</a></li> </ul> </div> <button class="accordion__button" id="acc-button-hazards" data-accordion="button" aria-controls="acc-panel-hazards" aria-expanded="false"> <span class="accordion__button__label"> Hazards </span> </button> <div 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aria-controls="acc-panel-environmental-science" aria-expanded="false"> <span class="accordion__button__label"> Environmental Science </span> </button> <div class="accordion__panel" id="acc-panel-environmental-science" data-accordion="panel" aria-labelledby="acc-button-environmental-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-ecology" data-accordion="button" aria-controls="acc-panel-ecology" aria-expanded="false"> <span class="accordion__button__label"> Ecology </span> </button> <div class="accordion__panel" id="acc-panel-ecology" data-accordion="panel" aria-labelledby="acc-button-ecology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/environmental-science/61/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Chemistry </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-atomic-theory-and-structure" data-accordion="button" aria-controls="acc-sub-panel-atomic-theory-and-structure" aria-expanded="false"> <span class="accordion__button__label"> Atomic Theory and Structure </span> </button> <div class="accordion__panel" id="acc-sub-panel-atomic-theory-and-structure" data-accordion="panel" aria-labelledby="acc-sub-button-atomic-theory-and-structure" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/chemistry/1/early-ideas-about-matter/49">Early Ideas about Matter</a></li> <li><a href="/en/library/chemistry/1/the-periodic-table-of-elements-i/52">The Periodic Table of Elements I</a></li> <li><a href="/en/library/chemistry/1/the-periodic-table-of-elements-ii/296">The Periodic Table of Elements II</a></li> <li><a href="/en/library/chemistry/1/the-periodic-table-of-elements-iii/297">The Periodic Table of Elements III</a></li> <li><a href="/en/library/chemistry/1/the-periodic-table-of-elements-iv/298">The Periodic Table of Elements IV</a></li> <li><a href="/en/library/chemistry/1/the-periodic-table-of-elements-v/299">The Periodic Table of Elements V</a></li> <li><a href="/en/library/chemistry/1/atomic-theory-i/50">Atomic Theory I</a></li> <li><a href="/en/library/chemistry/1/atomic-theory-ii/51">Atomic Theory II</a></li> <li><a href="/en/library/chemistry/1/atomic-theory-iii/223">Atomic Theory III</a></li> <li><a href="/en/library/chemistry/1/atomic-theory-iv/231">Atomic Theory IV</a></li> <li><a href="/en/library/chemistry/1/the-mole-and-atomic-mass/53">The Mole and Atomic Mass</a></li> </ul> </div> <button class="accordion__button" 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href="/en/library/chemistry/1/kinetic-molecular-theory/251">Kinetic-Molecular Theory</a></li> <li><a href="/en/library/chemistry/1/solutions/266">Solutions</a></li> <li><a href="/en/library/chemistry/1/water/267">Water</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-chemical-relationships" data-accordion="button" aria-controls="acc-sub-panel-chemical-relationships" aria-expanded="false"> <span class="accordion__button__label"> Chemical Relationships </span> </button> <div class="accordion__panel" id="acc-sub-panel-chemical-relationships" data-accordion="panel" aria-labelledby="acc-sub-button-chemical-relationships" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/chemistry/1/chemical-bonding/55">Chemical Bonding</a></li> <li><a href="/en/library/chemistry/1/stoichiometry/270">Stoichiometry</a></li> <li><a href="/en/library/chemistry/1/chemical-equations/268">Chemical Equations</a></li> <li class="current">Acids and Bases I</li> <li><a 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id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Chemical Relationships</em></strong> </span> <h1>Acids and Bases I: <sub><em>Definitions, pH and neutralization</em></sub></h1> <p class="byline">by Robin Marks, M.A.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/chemistry/1/acids-and-bases-i/271/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/chemistry/1/acids-and-bases-i/271/quiz">Quiz</a> </li> <li> <a href="/en/library/chemistry/1/acids-and-bases-i/271/resources">Teach with this</a> </li> </ul> </nav> </div> <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "AudioObject", "contentUrl": "https://www.visionlearning.com/img/library/moduleAudio/module_271.mp3", "description": "Recording of Acids and Bases I : Whether maintaining water quality in a fish tank or suffering from acid indigestion, we encounter the effects of acid-base chemistry in many common situations. This module explores acids and bases and describes how our understanding of acid-base chemistry has been refined over the centuries. The module explains how the pH scale indicates acidity. A table of pH values demonstrates how familiar substances range from extremely acidic to extremely basic. Also covered is a neutralization technique called titration.", "encodingFormat": "mp3", "name": "module_271.mp3" } </script> <div class="module_header_audio"> <div class="audio-player border border-radius"> <audio id="audio"> <source src="https://www.visionlearning.com/img/library/moduleAudio/module_271.mp3" type="audio/mpeg"> Your browser does not support the audio element. </audio> <div class="audio-player__title"> <p>Listen to this reading</p> <span class="audio-player__timestamp" id="timestamp"> 00:00 </span> </div> <div class="audio-player__controls" id="controls"> <button class="button button--icon-only" id="play-pause-button"> <span class="icon icon-play" aria-hidden="true"></span> </button> <div class="audio-player__progress" id="progress-bar" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-label="Use arrow keys to forward or rewind the audio" role="slider"> <div class="audio-player__progress__fill"> <span class="audio-player__thumb"></span> </div> </div> <div class="audio-player__volume-container"> <button id="mute-button"> <span class="icon icon-volume"></span> </button> <div class="audio-player__volume" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="100" aria-label="Use arrow keys to adjust volume" role="slider"> <div class="audio-player__volume__fill"> <span class="audio-player__thumb"></span> </div> </div> </div> </div> </div> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that you don’t need to be a professional scientist to make use of acid-base chemistry? When you eat too much of a spicy food, it is acid that puts the “burn” in heartburn. And when you seek relief through medication or baking soda in water, your goal is to bring about a chemical reaction called neutralization.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"> <li><p>The Arrhenius definition of an acid is a substance that loses a proton (H+) when it dissolves in water. Conversely, a base is a substance that releases an OH- ion when dissolved in water.</p></li> <li><p>The Brønsted -Lowry definition of an acid is a substance that donates a proton (H+). A base is then a substance that accepts a proton.</p></li> <li><p>pH measures the acidity of a solution, and is determined by the concentration of hydrogen ions</p></li> <li><p>A pH of 7 is considered neutral, a pH below that is acidic, above that is basic.</p></li> <li><p>Titration is a neutralization technique that can be used to determine the pH of the substance being neutralized.</p></li></ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt>[H+] </dt> <dd> "hydrogen ion concentration," which is measure of acidity. Square brackets indicate "concentration." </dd> <dt>mol </dt> <dd> the abbreviation of "mole" (the quantity that equals 6.02 × 1023)</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p><em>This is an updated version of the module</em> <a target="_blank" href="https://www.visionlearning.com/en/library/Chemistry/1/Acids-and-Bases/58"><em>Acids and Bases</em></a>.</p> <p>If you’ve ever cared for a pet fish, you know that you can’t just add plain tap water to the tank. If you do, you’ll throw off the chemistry of the <mark class="term" data-term="environment" data-term-def="The conditions that surround and affect an organism." data-term-url="/en/glossary/view/environment/8270">environment</mark> the fish needs to survive, and the fish may die. One important aspect of a fish’s environment is the acidity of the <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> it’s swimming in.</p><div class="figure"><figure><a title="Fish in an aquarium" href="/images/figure-images/271-a-2x.jpg"> <img src="/images/figure-images/271-a.jpg" alt="Fish in an aquarium"> </a> <figcaption><strong>Figure 1</strong>: The fish in this aquarium, like their relatives in lakes, rivers, and oceans, are sensitive to sudden pH changes in the water around them. When adding water to an aquarium, you need to make sure the new water will be at a pH close to the water already in the tank.</figcaption> </figure></div><p>Acidity is the quality that gives <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquids</mark> such as vinegar and lemon juice their lip-puckering taste. In fact, the term <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark> comes from the Latin term acere, which <mark class="term" data-term="mean" data-term-def="In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/mean/4221">means</mark> "sour”. The chemical opposites of acids are <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark>, <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compounds</mark> that often feel soapy or slippery and lend bitterness to foods such as walnuts and broccoli.</p><p>While there are many slightly different definitions of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> and <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark>, for purposes of this discussion of the fundamentals of acid/base chemistry, we’ll introduce you to two definitions: the Arrhenius definition and the Brønsted-Lowry definition. In addition, we will introduce you to the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> and to the <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> of neutralizing acids and bases, which will keep your fish healthy.</p> <p><section id="toc_1" class=""> <h2>The first chemical descriptions of acids and bases</h2></p> <p>People have known for centuries that there were substances like lemons and vinegar that shared that characteristic of being acere (sour). It was the Irish writer and amateur chemist <mark class="term" data-term="Robert Boyle" data-term-def="English chemist and theologian, born at Lismore Castle, Munster, Ireland (1627-1691). Boyle published on a broad array of topics, including chemistry,&hellip;" data-term-url="/en/glossary/view/Boyle%2C+Robert/4459">Robert Boyle</mark> in the mid-1660s, who first labeled substances as either <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> or alkalies (which we now call bases), according to the following characteristics:</p><p><b>Acids</b> taste sour, corrode metals, and change litmus (a dye that changes color based on acidity) red.</p> <p><b>Bases</b> taste bitter, feel slippery, and change litmus blue.</p> <p>Boyle also observed that some of the characteristics of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> can be counteracted by adding <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark>, and vice versa. While he and others tried to explain why acids and bases behave the way they do, the first reasonable definition of acids and bases would not be proposed until 200 years later.</p></section> <section id="toc_2"> <h2>The Arrhenius definition first explains acid/base chemistry</h2><p>In the late 1800s, the Swedish scientist Svante Arrhenius proposed that water can dissolve many compounds by separating them into their individual ions. Arrhenius suggested that acids are compounds that contain hydrogen and can dissolve in water to release hydrogen ions into solution. For example, hydrochloric acid (HCl) dissolves in water as follows:<div class="figure"><figure> $$HCl \text{ in water } \rightarrow H^+(aq) + Cl^-(aq)$$ </figure></div><p>(The "aq" in parenthesis stands for "aqueous," meaning that the ions are dissolved in a water-based solution.)</p></p><div class="figure"><figure><a title="Svante Arrhenius in his lab." href="https://www.visionlearning.com/images/figure-images/271-b-2x.jpg"> <img src="https://www.visionlearning.com/images/figure-images/271-b.jpg" alt="Svante Arrhenius in his lab."> </a> <figcaption><strong>Figure 2</strong>: Svante Arrhenius in his lab. <span class="credit">image © Richard Bergh</span></figcaption> </figure></div><p>In contrast, Arrhenius defined bases as substances that dissolve in water to release hydroxide ions (OH-) into solution. For example, a typical base according to the Arrhenius definition is sodium hydroxide (NaOH):<div class="figure"><figure> $$NaOH \text{ in water } \rightarrow Na^+ (aq)^+ OH^- (aq)$$ </figure></div><p>The Arrhenius definition of acids and bases explains a number of things. Arrheniusâ definition explains why all acids have similar properties to each other and, conversely, why all bases are similar. Acids all release H<sup>+</sup> into solution while bases all release OH<sup>-</sup>. The Arrhenius definition also explains Boyle's observation that acids and bases counteract each other. This idea, that a basic solution becomes less basic when mixed with an acid, and vice versa, is called neutralization - a concept weâll discuss further in this lesson.</p><p>Though Arrhenius helped explain the fundamentals of acid/base chemistry, his ideas have limits. For example, the Arrhenius definition does not explain why some substances, such as common baking soda (NaHCO<sub>3</sub>), can neutralize acids (thus acting like bases) even though they do not contain hydroxide ions.</p></p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc12154"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Svante Arrhenius proposed that bases release _____ when dissolved in water.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12154-0-option-a" name="quiz-option-12154" type="radio" value="H<sup>+</sup>" > <span class="option__label"> <span class="screen-reader-only">a.</span> H<sup>+</sup> </span> </label> <span class="quiz__response" id="response-12154-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12154-1-option-b" name="quiz-option-12154" type="radio" value="OH<sup>-</sup>" > <span class="option__label"> <span class="screen-reader-only">b.</span> OH<sup>-</sup> </span> </label> <span class="quiz__response" id="response-12154-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_3"> <h2>The Brønsted-Lowry definition gives a fuller picture of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> and bases</h2><p>In 1923, the Danish scientist <mark class="term" data-term="Johannes Brønsted" data-term-def="Danish physical chemist born in Varde (1879-1947). In 1906, Brønsted published his first paper on electron affinity. In 1923, he suggested&hellip;" data-term-url="/en/glossary/view/Br%C3%B8nsted%2C+Johannes/4526">Johannes Brønsted</mark> and the Englishman Thomas Lowry published independent yet similar papers that refined Arrhenius' <mark class="term" data-term="theory" data-term-def="A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and&hellip;" data-term-url="/en/glossary/view/theory/4854">theory</mark>. In Brønsted's words, "... <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> and <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark> are substances that are capable of splitting off or taking up hydrogen <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark>, respectively." The Brønsted-Lowry definition broadened the Arrhenius concept of acids and bases. </p><p>Like Arrhenius, Brønsted-Lowry defines <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> as any substances that can donate hydrogen <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark> to a <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> (under the Brønsted definition, acids are often referred to as <mark class="term" data-term="proton" data-term-def="A subatomic (ß link to atom) particle with a positive charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 1.672&hellip;" data-term-url="/en/glossary/view/proton/854">proton</mark> donors because an H+ ion - hydrogen minus its <mark class="term" data-term="electron" data-term-def="A subatomic particle with a negative charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 9.11 × 10<sup>-31</sup> kg. Electrons&hellip;" data-term-url="/en/glossary/view/electron/852">electron</mark> - consists of simply one proton). </p><p>The BrÃ¸nsted definition of bases is, however, quite different from the Arrhenius definition. BrÃ¸nsted defined a base as any substance that can accept a hydrogen ion. In essence, bases are the opposite of acids. NaOH, as we saw above, would still be considered a base because once dissolved in water, the OH<sup>-</sup> can accept an H<sup>+</sup> from an acid to form water. <div class="figure"><figure> $$NaOH \text{ in water } \rightarrow Na^+ (aq) + OH^- (aq)$$ </figure></div><div class="figure"><figure> $$OH^- + H^+ \rightarrow H_2O^-(aq)$$ </figure></div></p><p>The Brønsted-Lowry definition also explains why substances that do not contain OH<sup>-</sup> can also act like <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark>. Antacid tablets are a good example of this. If you look at the ingredients on a package of an antacid, you’ll likely see calcium carbonate, or CaCO<sub>3</sub>, among them. To understand why this <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">works</mark> as an antacid, take a moment to think about your favorite pizza (which, if it has tomato sauce on it, is rather acidic).</p><div class="figure"><figure> <a href="https://visionlearning.com/images/figure-images/271-c-2x.png" title=""> <span class="fa fa-search-plus"></span> <img src="https://visionlearning.com/images/figure-images/271-c.png" alt=""> </a> <figcaption> <strong>Figure 3</strong>: Antacid tablets with calcium carbonate release carbonate ions. The ions act as a base to absorb acidic hydrogen ions found in pizza and in your stomach. </figcaption> </figure></div><p>When you eat food (or even begin thinking about eating), your stomach produces hydrochloric acid, HCl, a strong acid that breaks down food to help in digestion. In the acid-water mixture in your stomach, the HCl dissociates, meaning it splits up into its constituent ions, in this case hydrogen and chloride:<div class="figure"><figure> $$HCl \text{ in water } \rightarrow H^+ (aq) + Cl^- (aq)$$ </figure></div></p><p>Those H+ ions make the solution in your stomach acidic. But too much of it, and youâll feel it as indigestion. So, you take an antacid, which dissociates to become calcium and carbonate ions:<div class="figure"><figure> $$CaCO_3 \rightarrow Ca^{+2} + {CO_3}^{-2}$$ </figure></div></p><p>The CO32- ion acts as an effective BrÃ¸nsted-Lowry base, able to mop up the excess H+ ions floating around in your stomach. Ah, relief.<div class="figure"><figure> $$2H^+ (aq) + {CO_3}^{-2} \rightarrow H_2CO_3$$ </figure></div></p><p>In this example, the carbonic acid formed (H<sub>2</sub>CO<sub>3</sub>) undergoes rapid decomposition to water and gaseous carbon dioxide:<div class="figure"><figure> $$H_2CO_3 \rightarrow H_2O + CO_2(g)$$ </figure></div></p><p>While this <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reaction</mark> reduces the acidity in your stomach, the gaseous carbon dioxide produced can accumulate in your stomach and eventually cause you to burp. So, all in all, best to avoid overeating foods like pizza.</p><p>Under both the Arrhenius and Brønsted-Lowry definitions, both <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> and <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark> are related to the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of hydrogen <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark> present. Acids increase the concentration of hydrogen <mark class="term" data-term="ion" data-term-url="/en/glossary/view/ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;">ions</mark>, while bases decrease the concentration of hydrogen ions (by accepting them). The acidity or basicity of something, therefore, can be measured by its hydrogen ion concentration.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc12167"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The Brønsted definition of a base is a substance that</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12167-0-option-a" name="quiz-option-12167" type="radio" value="(a) releases hydroxide ions" > <span class="option__label"> <span class="screen-reader-only">a.</span> (a) releases hydroxide ions </span> </label> <span class="quiz__response" id="response-12167-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12167-1-option-b" name="quiz-option-12167" type="radio" value="(b) can accept a hydrogen ion" > <span class="option__label"> <span class="screen-reader-only">b.</span> (b) can accept a hydrogen ion </span> </label> <span class="quiz__response" id="response-12167-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>pH: The measure of H<sup>+</sup> concentration</h2><p>In 1909, the Danish biochemist Sören Sörensen invented the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> for measuring acidity. Sörensen was studying the activity of enzymes—proteins that catalyze <mark class="term" data-term="chemical reaction" data-term-def="A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that&hellip;" data-term-url="/en/glossary/view/chemical+reaction/1547">chemical reactions</mark> in living things—and noticed that the acidity of the <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> affected the ability of the <mark class="term" data-term="enzyme" data-term-def="Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly&hellip;" data-term-url="/en/glossary/view/enzyme/1595">enzymes</mark> to catalyze <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reactions</mark>. At the time, there was no good way to articulate how acidic one <mark class="term" data-term="compound" data-term-def="A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances." data-term-url="/en/glossary/view/compound/1517">compound</mark> was compared to another. Frustrated by the lack of a measurement <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>, Sörensen invented the pH scale. While the exact meaning of pH remains debatable, some believe it stands for “power of hydrogen.” </p><p>No <mark class="term" data-term="matter" data-term-def="The substance that makes up physical objects." data-term-url="/en/glossary/view/matter/8264">matter</mark> what the letters stand for, <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> is a way of measuring the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of H+ <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark> in <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> that are available to participate in a <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reaction</mark>. (To review concentration, see the section on molarity in our module <a href="/library/module_viewer.php?mid=266">Solutions, <mark class="term" data-term="solubility" data-term-def="The extent to which a solid dissolves in a particular solvent." data-term-url="/en/glossary/view/solubility/7572">Solubility</mark>, and Colligative Properties</a>. The pH <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> is a logarithmic scale, meaning that for each increment of 1 on the scale, say the change from a pH of 2 to a pH of 3, the concentration of H <mark class="term" data-term="ion" data-term-url="/en/glossary/view/ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;">ions</mark> changes by a factor of ten. A pH of 2 has 1 x 10<sup>-2</sup> mol H<sup>+</sup>/L and a pH of 3 has 1 x 10<sup>-3</sup> mol H<sup>+</sup>/L.</p><p>Note that the exponent on the concentration is a negative number. For that reason, mathematically, pH is actually the inverse log of the concentration of H<sup>+</sup> in the solution:<div class="figure"><figure> $$pH = \text{-log }[H^+]$$ <figcaption>Note: Concentration is commonly abbreviated by using square brackets, thus [H<sup>+</sup>] = hydrogen ion concentration. When measuring pH, [H<sup>+</sup>] is in units of moles of H<sup>+</sup> per liter of solution.</figcaption> </figure></div></p><p>Don't be intimidated by the math! Even if you're not familiar with logarithms, this one is still fairly easy to understand. You can think of a logarithm as the <mark class="term" data-term="exponent" data-term-def="A number or expression written superscript to another number or expression, called the base, and indicating the power to which the&hellip;" data-term-url="/en/glossary/view/exponent/8759">exponent</mark> on the 10 in the [H<sup>+</sup>]. For example, a <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> with [H<sup>+</sup>] = 1 x 10<sup>-7</sup> moles/liter has a <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> equal to 7. (The pH is positive because we’re taking the negative log, -(-7), and the two minus signs become a positive. </p><p>Let’s think about water. At room temperature, pure water has a <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of 7, which <mark class="term" data-term="mean" data-term-def="In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/mean/4221">means</mark> that [H<sup>+</sup>] (the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of hydrogen ions) is 1x10<sup>-7</sup>, or 0.0000001. A pH of 7 is considered <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark>, meaning that [H<sup>+</sup>] and [OH<sup>-</sup>] are equal. </p><p>A <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of 1x10<sup>-7</sup>, or 0.0000001 mol/L might seem pretty small, but changes in concentration on either side of <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark> can make a big difference in the chemistry. When [H<sup>+</sup>] is greater than 10<sup>-7</sup> (for example, if it equals 1 x 10<sup>-6</sup>), the <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> is basic. If [H<sup>+</sup>] is less than 10<sup>-7</sup> (for example, if it equals 1 x 10<sup>-8</sup>), the solution is acidic.</p><p>If the <mark class="term" data-term="exponent" data-term-def="A number or expression written superscript to another number or expression, called the base, and indicating the power to which the&hellip;" data-term-url="/en/glossary/view/exponent/8759">exponents</mark> and <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentrations</mark> are confusing, think of it this way: Remember that when we’re dealing with a negative exponent, we’re talking about the number of zeros you put between the decimal and the 1. The more zeros, smaller the number gets, and the less H<sup>+</sup> you have in <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark>. </p><p>For example: 0.0000001 (1x10<sup>-7</sup>) is ten times larger than 0.00000001 (1x10<sup>-8</sup>). Since <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> is the measure of [H<sup>+</sup>], 1x10<sup>-8</sup> represents an [H<sup>+</sup>] that is ten times smaller than 1x10<sup>-7</sup>.</p><p>Now, compare the <mark class="term" data-term="exponent" data-term-def="A number or expression written superscript to another number or expression, called the base, and indicating the power to which the&hellip;" data-term-url="/en/glossary/view/exponent/8759">exponents</mark> on those two numbers: -7 and -8. If we take the negative sign away, we have the <mark class="term" data-term="value" data-term-def="A number that is assigned based on measurement or a calculation. In mathematics, an unknown value that is commonly represented by&hellip;" data-term-url="/en/glossary/view/value/8254">value</mark> of the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark>. 1x10-7 Is a pH of 7, and 1x10-8 is a pH of 8. So, contrary to what you might expect, a higher pH number represents a smaller [H+].</p><p>The presence of H<sup>+</sup> <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark> is what causes acidity, and conversely, the lack of H<sup>+</sup> (or presence of OH<sup>-</sup>) is what causes basicity. So as [H<sup>+</sup>] gets smaller (and the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> <mark class="term" data-term="value" data-term-def="A number that is assigned based on measurement or a calculation. In mathematics, an unknown value that is commonly represented by&hellip;" data-term-url="/en/glossary/view/value/8254">value</mark> gets higher), a <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> becomes less acidic, and more basic. Since 7 is a <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark> pH, a solution with a pH greater than 7 is basic, because it has an [H<sup>+</sup>] smaller than 1x10<sup>-7</sup>. By the same token, a solution with a pH of less than 7 is acidic, and has an [H<sup>+</sup>] larger than 1x10<sup>-7</sup>.</p><p>For example:</p> <p>For an [H<sup>+</sup>] of 1 x 10<sup>-3</sup>, the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> is 3 and the <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> is acidic.</p> <p>For an [H<sup>+</sup>] of 1 x 10<sup>-11</sup>, the pH is 11 and the solution is basic.</p> <p>The pH <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> ranges from 0 to 14. Substances with a pH from 0 to 7 are considered acidic. Substances with a pH greater than 7 and up to 14 are considered basic. Right in the middle, at pH = 7, are <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark> substances, for example, pure water. The relationship between [H<sup>+</sup>] and pH is shown in the table below alongside some common examples of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> and <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark> in everyday life.</p><div class="table-container"> <div class='"table-container"'><table class="table"> <thead> <tr> <th></th> <th><b>[H<sup>+</sup>]</b></th> <th><b>pH</b></th> <th><b>Example</b></th> </tr> </thead> <tbody> <tr> <td rowspan="7">Acids</td> <td>1 <font size="-2">X</font> 10<sup>0</sup></td> <td class="ph-00">0</td> <td>HCl </td> </tr> <tr> <td>1 x 10<sup>-1</sup></td> <td class="ph-01">1</td> <td>Stomach acid</td> </tr> <tr> <td>1 x 10<sup>-2</sup></td> <td class="ph-02">2 </td> <td>Lemon juice</td> </tr> <tr> <td>1 x 10<sup>-3</sup></td> <td class="ph-03">3 </td> <td>Vinegar</td> </tr> <tr> <td>1 x 10<sup>-4</sup></td> <td class="ph-04">4</td> <td>Soda</td> </tr> <tr> <td>1 x 10<sup>-5</sup></td> <td class="ph-05">5</td> <td>Rainwater</td> </tr> <tr> <td>1 x 10<sup>-6</sup></td> <td class="ph-06">6</td> <td>Milk</td> </tr> <tr> <td>Neutral</td> <td>1 x 10<sup>-7</sup></td> <td class="ph-07">7</td> <td>Pure water</td> </tr> <tr> <td rowspan="7">Bases</td> <td>1 x 10<sup>-8</sup></td> <td class="ph-08">8</td> <td>Egg whites</td> </tr> <tr> <td>1 x 10<sup>-9</sup></td> <td class="ph-09">9</td> <td>Baking soda</td> </tr> <tr> <td>1 x 10<sup>-10</sup></td> <td class="ph-10">10</td> <td>Tums<sup>Â®</sup> antacid</td> </tr> <tr> <td>1 x 10<sup>-11</sup></td> <td class="ph-11">11</td> <td>Ammonia</td> </tr> <tr> <td>1 x 10<sup>-12</sup></td> <td class="ph-12">12</td> <td>Mineral lime - Ca(OH)<sub>2</sub></td> </tr> <tr> <td>1 x 10<sup>-13</sup></td> <td class="ph-13">13 </td> <td>Drano<sup>Â®</sup></td> </tr> <tr> <td>1 x 10<sup>-14</sup></td> <td class="ph-14"> 14 </td> <td>NaOH</td> </tr> </tbody> </table></div> </div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc12180"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The higher the pH number, the __________ the concentration of H+ in a solution.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12180-0-option-a" name="quiz-option-12180" type="radio" value="lower" > <span class="option__label"> <span class="screen-reader-only">a.</span> lower </span> </label> <span class="quiz__response" id="response-12180-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12180-1-option-b" name="quiz-option-12180" type="radio" value="higher" > <span class="option__label"> <span class="screen-reader-only">b.</span> higher </span> </label> <span class="quiz__response" id="response-12180-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_5"> <h2>Neutralizing acids and bases</h2><p>Let’s go back to our earlier example of overindulging on pizza. The <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> table shows that the HCl in your stomach has a pH of 1, very acidic. It’s the amount of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark> in your stomach that makes you feel the “burn” in “heartburn.” The antacid tablets, remember, contain the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> calcium carbonate, CaCO<sub>3</sub>, which accounts for their pH of 10. When we add the CaCO<sub>3</sub> base to the HCl mixture, the resulting CO<sub>3</sub><sup>-2</sup> <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ion</mark> is able to <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> H<sup>+</sup> <mark class="term" data-term="ion" data-term-url="/en/glossary/view/ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;">ions</mark>, bringing the mixture closer to a <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark> pH of 7. This is a type of <mark class="term" data-term="neutralization" data-term-def="The chemical process of making a solution of acid or base into a neutral solution by adding either base or acid,&hellip;" data-term-url="/en/glossary/view/neutralization/1578">neutralization</mark> <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reaction</mark> in which a base is added to an acid to raise the pH (or vice versa).</p><p>We can also carry out a <mark class="term" data-term="neutralization" data-term-def="The chemical process of making a solution of acid or base into a neutral solution by adding either base or acid,&hellip;" data-term-url="/en/glossary/view/neutralization/1578">neutralization</mark> <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reaction</mark> in the laboratory. For example, we can add NaOH to a picture of HCl to neutralize the <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark>. In this case the neutralization reaction involves an H<sup>+</sup> from the acid and an OH<sup>-</sup> from the <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark>. (This is an instance in which the Arrhenius definition comes in handy). The two <mark class="term" data-term="ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;" data-term-url="/en/glossary/view/ion/853">ions</mark> combine to form a water <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark>, taking both the acidic and basic <mark class="term" data-term="ion" data-term-url="/en/glossary/view/ion" data-term-def="An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion&hellip;">ions</mark> out of <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark>.</p><p>The dissociation reactions are:<div class="figure"><figure> $$HCl + H_2O \rightarrow H^+(aq) + Cl^{-+}(aq)$$ </figure></div><p>And</p><div class="figure"><figure> $$NaOH + H_2O \rightarrow Na^+(aq) + OH^{-+}(aq)$$ </figure></div><p>As you can see from the equations, the acidic HCl releases H<sup>+</sup> into solution and the NaOH base releases OH<sup>-</sup>. If we mix the acid and base together, the H<sup>+</sup> ions combine with the OH<sup>-</sup> ions to make water, H<sub>2</sub>O:</p></p><div class="figure"><figure> $$H^+(aq) + OH^-(aq) \rightarrow H_2O$$ <p>When each H<sup>+</sup> from the acid has been paired with an OH<sup>-</sup> and neutralized, the solution will have a pH of 7. </p></figure></div></section> <section id="toc_6"> <h2>Titration: Using <mark class="term" data-term="neutralization" data-term-def="The chemical process of making a solution of acid or base into a neutral solution by adding either base or acid,&hellip;" data-term-url="/en/glossary/view/neutralization/1578">neutralization</mark> to determine the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of a solution</h2><p>Neutralization can also be used to determine the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of a <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark>. For example, let’s say you need to neutralize acidic runoff from a mining operation. You know that the particular mining <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> you’re looking at produces HCl, but you don’t know the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of HCl in the runoff. You can determine the HCl concentration by neutralizing a sample of the runoff with a solution of <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> that you do know the concentration of and keeping track of how much of the base solution was required. From there, you can calculate HCl concentration in the runoff. </p><p>The <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> of determining <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> by neutralizing a <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> of unknown <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> with one of known concentration is called <mark class="term" data-term="Titration" data-term-def="The process of determining the concentration of an ion in a solution by neutralizing it using a known concentration or amount&hellip;" data-term-url="/en/glossary/view/Titration/12229">titration</mark>. In the lab, <mark class="term" data-term="Titration" data-term-url="/en/glossary/view/Titration" data-term-def="The process of determining the concentration of an ion in a solution by neutralizing it using a known concentration or amount&hellip;">titration</mark> involves a setup with specific equipment that maintains the <mark class="term" data-term="accuracy" data-term-def="In science, the term accuracy describes how well a measurement approximates the theoretically correct value of that measurement, for example, how&hellip;" data-term-url="/en/glossary/view/accuracy/4222">accuracy</mark> of the process, because you need to know the starting <mark class="term" data-term="volume" data-term-def="The amount of space taken up by matter, commonly expressed in cubic centimeters (cm<sup>3</sup>) or milliliters (ml)." data-term-url="/en/glossary/view/volume/8515">volume</mark> of <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark> and the amount of <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> used. </p><div class="figure"><figure> <a href="https://visionlearning.com/images/figure-images/271-d-2x.png" title="The setup for a titration of HCl with NaOH."> <span class="fa fa-search-plus"></span> <img src="https://visionlearning.com/images/figure-images/271-d.png" alt="The setup for a titration of HCl with NaOH."> </a> <figcaption> <strong>Figure 4</strong>: The setup for a titration of HCl with NaOH. </figcaption> </figure></div><p>As seen in Figure X, 20 mL of the runoff <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> containing HCl has been measured out and placed in a flask. A burette (essentially a graduated cylinder with a stopcock at the bottom that allows you to add <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> in measured increments) is filled with 1M NaOH and positioned so that it is easy to add small quantities of base to the <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark>. (If you need to review molarity, see our module <a href="/library/module_viewer.php?mid=266">Solutions, <mark class="term" data-term="solubility" data-term-def="The extent to which a solid dissolves in a particular solvent." data-term-url="/en/glossary/view/solubility/7572">Solubility</mark>, and Colligative Properties</a>.</p><p>The HCl <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> also contains a small amount of a <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> called a <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> <mark class="term" data-term="indicator" data-term-def="A substance that, when added to an aqueous solution, has a color determined by the pH. If reactant is added&hellip;" data-term-url="/en/glossary/view/indicator/12228">indicator</mark>. An <mark class="term" data-term="indicator" data-term-url="/en/glossary/view/indicator" data-term-def="A substance that, when added to an aqueous solution, has a color determined by the pH. If reactant is added&hellip;">indicator</mark> is a substance that, when dissolved in water, will change color at a specific pH, indicating that the solution in the flask has reached that pH <mark class="term" data-term="value" data-term-def="A number that is assigned based on measurement or a calculation. In mathematics, an unknown value that is commonly represented by&hellip;" data-term-url="/en/glossary/view/value/8254">value</mark>. In this case, you would use an indicator that changes color at pH 7, because you want to know when the <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark> solution has been completely neutralized.</p><p>To do the <mark class="term" data-term="Titration" data-term-def="The process of determining the concentration of an ion in a solution by neutralizing it using a known concentration or amount&hellip;" data-term-url="/en/glossary/view/Titration/12229">titration</mark>, you note the starting <mark class="term" data-term="volume" data-term-def="The amount of space taken up by matter, commonly expressed in cubic centimeters (cm<sup>3</sup>) or milliliters (ml)." data-term-url="/en/glossary/view/volume/8515">volume</mark> of 1M NaOH. Let’s say it’s 500 mL. You slowly add <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> just until the point where the <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> in the flask changes color, and then stop. Then note volume of base after addition to the <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark>, let’s say it’s 460 mL. </p> <p>500 mL starting – 460 mL ending = 40 mL 1M NaOH added to the acid in the flask </p><p>Because we know the concentration of the NaOH, we can determine how many moles of it are in our 40 mL<div class="figure"><figure> $$\frac{\text{1mol } NaOH}{\text{1L } NaOH} = \frac{\text{x mol } NaOH}{\text{0.40L } NaOH}$$ </figure></div></p><p>Solving for x:<div class="figure"><figure> $$\text{0.40L }NaOH \times \frac{\text{1mol }NaOH}{\text{1L }NaOH} = \text{ x mol } NaOH$$ </figure></div><p>x = 0.40 mol NaOH added</p><p>We know that in water, NaOH releases a single OH-, and HCl releases a single H+, which means that for every mole of HCl, one mole of NaOH is required to neutralize it. Since we used 0.40 mol of NaOH in the titration, there must be 0.40 mol of HCl in the flask.</p></p><p>To figure out the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of the HCl, we then take the number of <mark class="term" data-term="mole" data-term-def="An amount equal to Avogadro's number, or 6.02 × 10<sup>23</sup>. One mole of atoms is equal to 6.02 × 10<sup>23</sup> atoms." data-term-url="/en/glossary/view/mole/1515">moles</mark> and divide it by the volume:</p><div class="figure"><figure> $$\frac{0.40mol}{0.20L} = 2mol/L$$ <figcaption>Concentration of HCl</figcaption> </figure></div><p>Now we can see that the <mark class="term" data-term="concentration" data-term-def="The amount of one substance in relation to other components within a given area." data-term-url="/en/glossary/view/concentration/8733">concentration</mark> of HCl in the runoff <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> is 2 mol/L. If the mine produces 1000 L of runoff, we know that runoff will contain 2 mol HCl/L, and therefore will require 2000 mol of <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">base</mark> to be neutralized. </p><p>Let’s return to the real-life example of our fish tank. Over time, plants, rocks, and the fish themselves will alter the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of the water. Most fish can adjust to a pH that changes slowly over time, but are very sensitive to sudden changes in pH. So when it’s time to clean the tank and add new water, we want to add water that is near the pH of what the fish have been swimming in. </p><p>If you’ve ever performed this task, you did a <mark class="term" data-term="Titration" data-term-def="The process of determining the concentration of an ion in a solution by neutralizing it using a known concentration or amount&hellip;" data-term-url="/en/glossary/view/Titration/12229">titration</mark> without even knowing it! In this case, you may not be trying to reach a <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of 7, but instead, you want to make a batch of tap water that matches the existing pH. To help with that effort, you can use a pH testing kit. Instead of a proper <mark class="term" data-term="Titration" data-term-url="/en/glossary/view/Titration" data-term-def="The process of determining the concentration of an ion in a solution by neutralizing it using a known concentration or amount&hellip;">titration</mark> setup, you’ll have a bucket of water and an aquarium pH testing kit. The kit contains a pH <mark class="term" data-term="Test" data-term-def="This is a test glossary term." data-term-url="/en/glossary/view/Test/12984">test</mark> <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark>, a color reference card, an acidic solution and a basic solution.</p><div class="figure"><figure> <a href="https://visionlearning.com/images/figure-images/271-e-2xjpg" title=""> <span class="fa fa-search-plus"></span> <img src="https://visionlearning.com/images/figure-images/271-e.jpg" alt=""> </a> <figcaption> <strong>Figure 5</strong>: an aquarium test kit contains a pH tester solution containing an indicator, a color reference card, and acidic and basic solutions. The acidic and basic solutions are used to titrate new water to be added to the tank, bringing it to a value that is within an acceptable pH range. <span class="credit">image © </span> </figcaption> </figure></div><p>First, you <mark class="term" data-term="Test" data-term-def="This is a test glossary term." data-term-url="/en/glossary/view/Test/12984">test</mark> the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> of a small sample of the water that was in the tank by adding a few drops of the pH testing <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark>, which contains a pH <mark class="term" data-term="indicator" data-term-def="A substance that, when added to an aqueous solution, has a color determined by the pH. If reactant is added&hellip;" data-term-url="/en/glossary/view/indicator/12228">indicator</mark>. You can then compare the color of the <mark class="term" data-term="indicator" data-term-url="/en/glossary/view/indicator" data-term-def="A substance that, when added to an aqueous solution, has a color determined by the pH. If reactant is added&hellip;">indicator</mark> to the color reference card. The different colors on the card indicate color changes associated with very subtle differences in pH around the <mark class="term" data-term="value" data-term-def="A number that is assigned based on measurement or a calculation. In mathematics, an unknown value that is commonly represented by&hellip;" data-term-url="/en/glossary/view/value/8254">value</mark> at which the indicator changes color. </p><p>Let’s say the <mark class="term" data-term="pH" data-term-def="A symbol representing a measure of the effective concentration of hydrogen ions in a solution, pH = -log [H<sup>+</sup>]. pH&hellip;" data-term-url="/en/glossary/view/pH/1577">pH</mark> is 5.5, which is a bit acidic. Now that you know the pH of the water in the tank, you can fill a bucket with the <mark class="term" data-term="volume" data-term-def="The amount of space taken up by matter, commonly expressed in cubic centimeters (cm<sup>3</sup>) or milliliters (ml)." data-term-url="/en/glossary/view/volume/8515">volume</mark> of new tap water you want to add, and use the <mark class="term" data-term="Test" data-term-def="This is a test glossary term." data-term-url="/en/glossary/view/Test/12984">test</mark> <mark class="term" data-term="solution" data-term-def="A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a&hellip;" data-term-url="/en/glossary/view/solution/1571">solution</mark> again to determine the pH. If the pH is a <mark class="term" data-term="neutral" data-term-def="Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved&hellip;" data-term-url="/en/glossary/view/neutral/855">neutral</mark> 7 like pure water, it’s too basic, and you’ll need to titrate it with a bit of the acidic solution, testing small samples of the water as you add <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark>, until the color indicates the pH you want. Once you’ve gotten the pH of the new water where you want it, you can add it to the tank knowing that you won’t give your fish a pH shock. </p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc12201"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Titration can be used to determine the pH of a substance that is being neutralized.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12201-0-option-a" name="quiz-option-12201" type="radio" value="true" > <span class="option__label"> <span class="screen-reader-only">a.</span> true </span> </label> <span class="quiz__response" id="response-12201-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12201-1-option-b" name="quiz-option-12201" type="radio" value="false" > <span class="option__label"> <span class="screen-reader-only">b.</span> false </span> </label> <span class="quiz__response" id="response-12201-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Robin Marks, M.A. “Acids and Bases I” Visionlearning Vol. CHE-4 (9), 2020. </em> </p> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_1">The first chemical descriptions of acids and bases</a> </li> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_2">The Arrhenius definition first explains acid/base chemistry</a> </li> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_3">The Brønsted-Lowry definition gives a fuller picture of acids and bases</a> </li> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_4">pH: The measure of H+ concentration</a> </li> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_5">Neutralizing acids and bases</a> </li> <li><a href="/en/library/chemistry/1/acids-and-bases-i/271#toc_6">Titration: Using neutralization to determine the pH of a solution</a> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. 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Acids and Bases I | Chemistry | Visionlearning