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href="../zinc/chemistry.html">Zinc</a></li> <li class="pure-menu-item d"><a class="pure-menu-link d" href="../zirconium/chemistry.html">Zirconium</a></li> </ul> </div> </div>  <div class="pure-g"> <div class="pure-u-1"> <div class="pure-menu pure-menu-open pure-menu-horizontal centre" role="navigation" style="background: #000 url(../_media/elements/discharge/K.png) repeat-y center; background-size:contain;"> <span><a class="pure-menu-heading" href="https://winter.group.shef.ac.uk/webelements/"><img height="30" src="../_media/icons/logo_60.png" alt="WebElements logo"></a> <a class="white" href="./">Potassium - <sub>19</sub>K</a>  <audio id="myAudio_f"> <source src="../_media/elements/snds_f/K.mp3" type="audio/mpeg">Your user agent does not support the HTML5 Audio element. </audio> <button class="pure-button s_button" style=" display: inline;" type="button" onclick="audf_play_pause()"> 🔊  </button> <script> function audf_play_pause() { var myAudiof = document.getElementById("myAudio_f"); if (myAudiof.paused) { myAudiof.play(); } else { myAudiof.pause(); }} </script></span> </div> </div> </div> <div id="main">  <div class="pure-u-1 pure-u-sm-1-1"> <div class="pure-menu pure-menu-horizontal pure-menu-scrollable"> <a href="#" class="pure-menu-link pure-menu-heading">▸▸</a> <ul class="pure-menu-list"> <li class="pure-menu-item">🇬🇧 Potassium</li> <li class="pure-menu-item">🇺🇦 Калій</li> <li class="pure-menu-item">🇨🇳 鉀</li> <li class="pure-menu-item">🇳🇱 Kalium</li> <li class="pure-menu-item">🇫🇷 Potassium</li> <li class="pure-menu-item">🇩🇪 Kalium</li> <li class="pure-menu-item">🇮🇱 אשלגן</li> <li class="pure-menu-item">🇮🇹 Potassio</li> <li class="pure-menu-item">🇯🇵 カリウム</li> <li class="pure-menu-item">🇵🇹 Potássio</li> <li class="pure-menu-item">🇪🇸 Potasio</li> <li class="pure-menu-item">🇸🇪 Kalium</li> <li class="pure-menu-item">🇷🇺 Калий</li> </ul> </div> </div> <div class="pure-g"> <div class="pure-u-1 pure-u-sm-1-1"> <div class="google_navbar_positioning"> <form action="https://www.google.com" id="cse-search-box"> <div> <input type="hidden" name="cx" value="partner-pub-9334432533380510:6223510783"> <input type="hidden" name="ie" value="UTF-8"> <input type="text" name="q" size="28"> <input type="submit" name="sa" value="Search"> </div> </form> <script> </script> </div> </div> </div> <main> <div class="pure-g"> <div class="pure-u-1 pure-u-sm-1-1"> <h1 class="s">Potassium - <sub><small>19</small></sub>K: reactions of elements</h1> <div class="pure-menu pure-menu-horizontal pure-menu-scrollable"> <ul class="pure-menu-list z_menu"> <li class="pure-menu-item s"><a href="../potassium/" class="pure-menu-link">▸▸ K Essentials</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/physics.html">Physical properties</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/atoms.html">Electron shell data</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/atom_sizes.html">Atom sizes</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/electronegativity.html">Electronegativity</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/isotopes.html" >Isotopes and NMR</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/crystal_structure.html">Crystal structure</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/thermochemistry.html">Thermochemistry</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/history.html">History</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/uses.html">Uses</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/geology.html">Geology</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/biology.html">Biology</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/compounds.html">Binary compounds</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/compound_properties.html" >Compound properties</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/chemistry.html">Element reactions</a></li> <li class="pure-menu-item s"><a class="pure-menu-link" href="../potassium/contents.html">List all K properties</a></li> </ul> </div> </div> </div> <h2 class="s">Reaction of potassium with air</h2> <p class="p_first">Potassium is very soft and easily cut. The resulting surface is bright and shiny. However, this surface soon tarnishes because of reaction with oxygen and moisture from the air. If potassium is burned in air, the result is mainly formation of orange potassium superoxide, KO<sub>2</sub>.</p> <p class="equation">K(s) + O<sub>2</sub>(g) → KO<sub>2</sub>(s)</p> <h2 class="s">Reaction of potassium with water</h2> <p class="p_first">Potassium metal reacts very rapidly with water to form a colourless solution of potassium hydroxide (KOH) and hydrogen gas (H<sub>2</sub>). The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic. Early in the reaction, the potassium metal becomes so hot that it catches fire and burns with a characteristic pale lilac colour. The reaction is slower than that of rubidium (immediately below potassium in the periodic table), but faster than that of sodium (immediately above potassium in the periodic table).</p> <p>2K(s) + 2H<sub>2</sub>O → 2KOH(aq) + H<sub>2</sub>(g)</p> <h2 class="s">Reaction of potassium with the halogens</h2> <p class="p_first">Potassium metal reacts vigorously with all the halogens to form potassium halides. So, it reacts with fluorine, F<sub>2</sub>, chlorine, Cl<sub>2</sub>, bromine, I<sub>2</sub>, and iodine, I<sub>2</sub>, to form respectively potassium(I) bromide, KF, potassium(I) chloride, KCl, potassium(I) bromide, KBr, and potassium(I) iodide, KI.</p> <p class="equation">2K(s) + F<sub>2</sub>(g) → KF(s)</p> <p class="equation">2K(s) + Cl<sub>2</sub>(g) → KCl(s)</p> <p class="equation">2K(s) + Br<sub>2</sub>(g) → KBr(s)</p> <p class="equation">2K(s) + I<sub>2</sub>(g) → KI(s)</p> <h2 class="s">Reaction of potassium with acids</h2> <p class="p_first">Potassium metal dissolves readily in dilute sulphuric acid to form solutions containing the aquated K(I) ion together with hydrogen gas, H<sub>2</sub>.</p> <p class="equation">2K(s) + H<sub>2</sub>SO<sub>4</sub>(aq) → 2K<sup>+</sup>(aq) + SO<sub>4</sub><sup>2-</sup>(aq) + H<sub>2</sub>(g)</p> <h2 class="s">Reaction of potassium with bases</h2> <p class="p_first">Potassium metal reacts very rapidly with water to form a colourless basic solution of potassium hydroxide (KOH) and hydrogen gas (H<sub>2</sub>). The reaction continues even when the solution becomes basic. The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic. Early in the reaction, the potassium metal becomes so hot that it catches fire and burns with a characteristic pale lilac colour. The reaction is slower than that of rubidium (immediately below potassium in the periodic table), but faster than that of sodium (immediately above potassium in the periodic table). 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