Question

A base which is not alkali

• A. Caustic potash
• B. Copper hydroxide
• C. Ammonium hydroxide

Answer 1

The correct option is B

Copper hydroxide

Alkalis are the bases that are soluble hydroxides while the rest of the bases are insoluble in water.

Explanation of the correct option :

The correct option is B).

1. Copper hydroxide ($\mathrm{Cu}{\left(\mathrm{OH}\right)}_2$) is a base as it hydroxide ions (${\mathrm{OH}}^{-}$) to release.
2. But, Copper hydroxide is insoluble in water. Hence, it is not an alkali
3. Hence, a base that is not alkali is Copper hydroxide.

Explanation of the incorrect options :

Option A: Caustic potash is $\mathrm{KOH}$. Potassium (K) belongs to group I (alkali metals) and hydroxides of group I are soluble in water. Hence, caustic potash is an alkali.

Option C: Ammonium hydroxide (${\mathrm{NH}}_4\mathrm{OH}$) is soluble in water. Hence, it is an alkali.

Hence, A base that is not alkali is (B) Copper hydroxide.