The chemical names of potassium hydroxide and sodium hydroxide are KOH and NaOH, respectively. Neither of these chemicals has any nutritional uses, as both would be extraordinarily dangerous to take internally. While they are interchangeable for many purposes, there are slight differences between the two in terms of chemistry and practical application.
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Potassium hydroxide and sodium hydroxide are both caustic bases formed from an alkali metal ionically bound to a hydroxide group. The metal in potassium hydroxide is heavier than the metal in sodium hydroxide. Potassium has an atomic weight of 39.10 and sodium has an atomic weight of 22.99. This weight difference reflects the difference in the number of protons in each metal. Potassium has 19 protons and sodium has only 11.
Differences in Reactivity
Like all strong bases, the reaction of both KOH and NaOH with water is strongly exothermic. Both reactions generate heat and give off hydrogen. However, the difference between NaOH and KOH is that the KOH and water reaction is slightly less exothermic.
KOH is cheaper than NaOH. The difference in cost is why there are more industrial applications for KOH than NaOH. KOH is used to make potassium permanganate, potassium phosphate and potassium carbonate. It is also used in fertilizers and soap manufacturing. Since KOH is more conductive than NaOH, it is used as an electrolyte in chemical batteries.
On the other hand, NaOH is favored in domestic applications, such as drain cleaning and hair straightening. It is also used in petroleum refining, paper manufacture, chocolate & cocoa processing. Food preparation uses include lutefisk and pretzel making.
KOH solutions leave a white or translucent stain, whereas NaOH solutions leave a yellow stain.
KOH is more soluble in water. While only 100 g of NaOH will dissolve in 100 ml of water, 121 g of KOH will dissolve in the same amount of water under the same conditions. KOH is also more soluble in methanol or ethanol than NaOH.