Question

Q8. A hydroxide sparingly soluble in water is

• A. Magnesium hydroxide
• B. Ferrous hydroxide
• C. Ferric hydroxide
• D. Calcium hydroxide

Answer 1

The correct option is D

Calcium hydroxide

The explanation for the correct option:

(D) Calcium hydroxide:

• Calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$is sparingly soluble in water because its dissociation in water is large enough and hydration enthalpy is low so according to the dissolution reaction:

$\underset{\mathrm{calcium}\mathrm{hydroxide}}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)}\to \underset{\mathrm{calcium}\mathrm{ions}}{{\mathrm{Ca}}^{2+}}+\underset{\mathrm{hydroxide}\mathrm{ion}}{2{\mathrm{OH}}^{-}}$

The explanation for incorrect options:

(A) Magnesium hydroxide is soluble in water but very slightly.

(B) Ferrous hydroxide is a compound that is insoluble in water.

(C) Ferric hydroxide is also insoluble when it comes to water.

Calcium hydroxide is sparingly soluble in water. Thus option D is correct.