Difference Between Sodium Hydroxide and Potassium Hydroxide

Sodium Hydroxide vs Potassium Hydroxide
 

Sodium Hydroxide and Potassium Hydroxide share some similar features though, there exists certain differences between them. Potassium Hydroxide and Sodium Hydroxide are both strong alkaline hydroxides, formed from the metallic ions of the same group in the periodic table. In the chemical point of view, they are both inorganic compounds, strong bases, and having highly corrosive properties. They are slightly similar to each other in appearance, chemical properties, and reactivity with acids. But there are slight differences in their chemistry and practical applications.

In industrial applications, one is an alternative for another. But, Sodium hydroxide is relatively abundant and cheaper than Potassium hydroxide. Due to the cost factor, Sodium hydroxide is mostly used in many applications. But Potassium hydroxide has its unique properties too.

What is Sodium Hydroxide (NaOH)?

Sodium hydroxide is a white solid, strong base, metallic hydroxide. Sodium hydroxide is commercially available in the form of granules, flakes, pellets and 50% (w/w) as a saturated solution with water. Sodium hydroxide is famous as “caustic soda” in industrial applications. It is highly soluble in water, partially soluble in ethanol and methanol and insoluble in non-polar solvents. A considerable amount of heat is released when sodium hydroxide solid is dissolved in water in water. This is because it is a highly exothermic reaction.

Difference Between Sodium Hydroxide and Potassium Hydroxide

What is Potassium Hydroxide (KOH)?

Potassium hydroxide is an inorganic metallic compound that has the chemical formula KOH, and it is also known as “caustic potash.” For chemists, it is a valuable strong base and it has so many industrial applications too. This compound is commercially available as yellowish or white pellets. It becomes very sticky by absorbing water as it is highly hygroscopic and it is difficult to dehydrate.

Similar to NaOH, dissolving KOH in water is highly exothermic. Highly concentrated potassium hydroxide solutions are extremely dangerous; even the lower concentrations (0.5%) are irritant to the skin and above 2.0% levels are corrosive.

Sodium Hydroxide vs Potassium Hydroxide

What is the difference between Sodium Hydroxide and Potassium Hydroxide?

• Physical properties:

Molecular weight:

They are the hydroxides of two consecutive members of group I metals: Sodium (Na) and Potassium (K).

• Molecular weight of potassium hydroxide is 56.11 g mol−1

• Molecular weight of sodium hydroxide is 39. 9971 g mol−1

• Molecular weight of potassium hydroxide is higher than that of sodium hydroxide because potassium is in period 3 while Sodium is in group 2 in the periodic table.

Electrical conductivity:

• Potassium hydroxide is more conductive than sodium hydroxide. Therefore, KOH is used as an electrolyte in chemical batteries.

Solubility:

• Potassium hydroxide (KOH) is more soluble in water than Sodium hydroxide (NaOH).

• About 121 g of KOH is soluble in 100 ml of water, compared to 100 g of NaOH in 100 ml of water.

• Reactivity with water:

• The reaction of potassium hydroxide is less exothermic than the reaction of sodium hydroxide with water.

• Cost:

• Potassium hydroxide is more expensive than sodium hydroxide.

• Industrial applications:

In most of the situations, potassium hydroxide and sodium hydroxide can be used interchangeably.

• Potassium Hydroxide:

• Potassium hydroxide is used in soap manufacturing and in fertilizer industry.

• Potassium hydroxide is also used to make potassium permanganate and potassium carbonate.

• Sodium Hydroxide:

• Sodium hydroxide is a base for chemists and it is very important in paper manufacturing process.

• In addition, it has so many other usages in food industry, cosmetic industry, and many more. For example, for hair straightening, soap making, cleaning, petroleum refining, and for animal carcasses dissolving.

 

Images Courtesy: Sodium hydroxide and potassium hydroxide via Wikicommons (Public Domain)