Caustic soda and potassium hydroxide are classified as which type of substance?

• A. Acids
• B. Salts
• C. Bases
• D. Oxides

Answer: (C)

Caustic soda, also known as sodium hydroxide (NaOH), and potassium hydroxide (KOH) are classified as bases due to their ability to accept protons or donate electron pairs in chemical reactions. Bases are characterized by their bitter taste, slippery feel, and capacity to neutralize acids. When dissolved in water, both caustic soda and potassium hydroxide dissociate into hydroxide ions (OH⁻), which are key indicators of a basic solution. This formation of hydroxide ions is what establishes their basicity and distinguishes them from other types of substances such as acids, which release hydrogen ions (H⁺) in solution.

In contrast, acids typically have a sour taste and can react with metals and carbonates, producing hydrogen gas or carbon dioxide. Salts are formed from the neutralization reaction of an acid and a base but do not inherently possess the properties of bases. Oxides can refer to a broader category of compounds where oxygen is bonded to another element but do not necessarily imply basic or acidic characteristics on their own.

Thus, due to their ability to increase the concentration of hydroxide ions in solution, caustic soda and potassium hydroxide are correctly categorized as bases.