Question

Q5. Gelatinous white precipitate soluble in excess of Ammonium hydroxide are of

• A. Calcium hydroxide
• B. Zinc hydroxide
• C. Magnesium hydroxide
• D. Lead hydroxide

Answer 1

The correct option is B

Zinc hydroxide

Explanation for correct option:

(B) The reaction of Zinc sulphate with Ammonium hydroxide is:

$\underset{\mathrm{zinc}\mathrm{sulphate}}{{\mathrm{ZnSO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{ammonium}\mathrm{hydroxide}}{4{\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{l}\right)}\to \underset{}{{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4}+\underset{\mathrm{zinc}\mathrm{hydroxide}}{\mathrm{Zn}{\left(\mathrm{OH}\right)}_2}$

Explanation for incorrect options:

(A) In the reaction of Ammonium hydroxide with that of Calcium hydroxide, no gel-like precipitate is formed.

(C) Magnesium hydroxide does not form any gelatinous white precipitate in excess of Ammonium hydroxide.

(D) Lead hydroxide also forms no such gelatinous precipitate.

Zinc hydroxide forms gelatinous white precipitate soluble in excess of Ammonium hydroxide. Thus Option b is correct.