Main Difference – Potassium Hydroxide vs Sodium Hydroxide
Sodium and potassium are highly reactive chemical elements that can be found in group 1 of the periodic table and are also known as alkali metals. They are s block elements because they have their valence electron in the outermost s orbital. Both sodium and potassium are very useful chemical elements because they form a wide variety of chemical compounds. Potassium hydroxide and Sodium Hydroxide are two such compounds. They belong to the group known as alkali metal hydroxide. Alkali hydroxides are chemical compounds containing a group 1 metal cation and a –OH anion. These are ionic compounds. These hydroxides are strong bases and are very corrosive. The main difference between Potassium hydroxide and Sodium Hydroxide is that Potassium hydroxide has a potassium cation and a -OH anion whereas Sodium Hydroxide has a sodium cation and –OH anion.
Key Areas Covered
1. What is Potassium Hydroxide
– Definition, Chemical Properties, Applications
2. What is Sodium Hydroxide
– Definition, Chemical Properties, Applications
3. Similarities Between Potassium Hydroxide and Sodium Hydroxide
– Outline of Common Features
4. What is the Difference Between Potassium Hydroxide and Sodium Hydroxide
– Comparison of Key Differences
Key Terms: Alkali, Anion, Base, Cation, Caustic Potash, Caustic Soda, Deliquescence, KOH, Metal Hydroxide, NaOH, Potassium, Potassium Hydroxide, Sodium, Sodium Hydroxide
What is Potassium Hydroxide
Potassium hydroxide is an alkali metal having the chemical formula KOH. The common name of potassium hydroxide is caustic potash. At room temperature, it is a colorless solid and is a strong base. Therefore, it has many industrial and laboratory applications.
The molar mass of potassium hydroxide is 56.11 g/mol. It is an odorless solid that is very deliquescent. (Deliquescent substances are solid matter that can get dissolved by absorbing water vapor. The resulting solution is an aqueous solution. This process is known as deliquescence. These deliquescent substances have a high affinity for water). The melting point of potassium hydroxide is 360 °C and the boiling point is 1,327 °C.
Figure 1: Potassium Hydroxide Pellets
Potassium hydroxide is commercially available as translucent pellets and when these pellets are exposed to open air, they become tacky. Dissolution of potassium hydroxide in water is highly exothermic. Higher concentrations of potassium hydroxide are corrosive whereas moderate concentrations can cause skin irritations. Potassium hydroxide exhibits a high thermal stability.
Applications
- As a cleaner (potassium hydroxide can be found in many soaps, shampoos, etc.)
- As a pH regulator (it is a strong alkali and can control acidity)
- Medicinal applications (to diagnose fungal diseases)
- In common household products (alkaline batteries contain potassium hydroxide)
- As a food additive (as a stabilizer)
What is Sodium Hydroxide
Sodium hydroxide is an alkali metal having the chemical formula NaOH. The common name for sodium hydroxide is caustic soda. It is an ionic compound containing sodium cations and –OH anions. It is a strong base.
The molar mass of sodium hydroxide is 39.99 g/mol. At room temperature, it appears as white, waxy crystals which are opaque. Sodium hydroxide is odorless. The melting point of sodium hydroxide is 318 °C and the boiling point is 1,388 °C.
Figure 2: Sodium Hydroxide Pellets
Sodium hydroxide is highly alkali and can cause severe burns. It is highly water soluble and is hygroscopic. This means, sodium hydroxide can absorb water vapor and carbon dioxide from the atmosphere. Dissolution of sodium hydroxide in water is highly exothermic.
Applications
- Cleaning and disinfectant products (used in manufacturing of many soaps and detergents)
- Pharmaceutical and medical applications (used in manufacture of medicine such as aspirin)
- Water treatment (to control water acidity)
- Wood and paper products (to dissolve unwanted material in wood)
- Food products (Ex: used to remove skin of tomatoes)
Similarities Between Potassium Hydroxide and Sodium Hydroxide
- Both are alkali metal hydroxides.
- Both are strong bases.
- Both can cause skin irritations;
- Both are water soluble.
- Reaction with water is highly exothermic for both compounds.
- Both can absorb water vapor from the air.
Difference Between Potassium Hydroxide and Sodium Hydroxide
Definition
Potassium Hydroxide: Potassium hydroxide is an alkali metal having the chemical formula KOH.
Sodium Hydroxide: Sodium hydroxide is an alkali metal having the chemical formula NaOH.
Molar Mass
Potassium Hydroxide: The molar mass of potassium hydroxide is 56.11 g/mol.
Sodium Hydroxide: The molar mass of sodium hydroxide is 39.99 g/mol.
Melting Point and Boiling Point
Potassium Hydroxide: The melting point of potassium hydroxide is 360 °C and the boiling point is 1,327 °C.
Sodium Hydroxide: The melting point of sodium hydroxide is 318 °C and the boiling point is 1,388 °C.
Cation
Potassium Hydroxide: Potassium hydroxide contains potassium ion as the cation.
Sodium Hydroxide: Sodium hydroxide contains sodium ion as the cation.
Water Dissolution
Potassium Hydroxide: Potassium hydroxide is less soluble in water.
Sodium Hydroxide: Sodium hydroxide is highly soluble in water.
Conclusion
Potassium hydroxide and sodium hydroxide are strong bases. Both are hydroxides of alkali metals. The main difference between Potassium hydroxide and Sodium Hydroxide is that Potassium hydroxide has a potassium cation and a -OH anion whereas Sodium Hydroxide has a sodium cation and –OH anion.
Reference:
1. “Sodium Hydroxide | Uses, Benefits, and Chemical Safety Facts.” ChemicalSafetyFacts.org, 22 Sept. 2017, Available here.
2. “Potassium hydroxide.” Wikipedia, Wikimedia Foundation, 15 Jan. 2018, Available here.
Image Courtesy:
1. “Potassium hydroxide” By Walkerma assumed. Own work assumed (based on copyright claims) (Public Domain) via Commons Wikimedia
2. “Sodium hydroxide by Danny S. – 001” By Danny S. – Own work (CC BY-SA 3.0) via Commons Wikimedia
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