Question

Bleaching powder can be prepared by reacting:

• A. Caustic soda with chlorine
• B. Washing soda with chlorine
• C. Baking soda with chlorine
• D. Slaked lime with chlorine

Answer 1

The correct option is D

Slaked lime with chlorine

Explanation for the correct option:

(D) Slaked lime with chlorine

Slaked lime $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ on reacting with chlorine $\left({\mathrm{Cl}}_2\right)$ produces bleaching powder $\left(\mathrm{Ca}{\left(\mathrm{OCl}\right)}_2\right)$ and water $\left({\mathrm{H}}_2\mathrm{O}\right)$.

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)\underset{}{\to }\mathrm{Ca}{\left(\mathrm{OCl}\right)}_2\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Explanation for the incorrect option(s):

(A) Caustic soda with chlorine

Caustic soda $\left(\mathrm{NaOH}\right)$ on reaction with chlorine produces sodium chloride $\left(\mathrm{NaCl}\right)$, sodium hypochlorite$\left({\mathrm{NaClO}}_3\right)$, and water.

$3{\mathrm{Cl}}_2\left(\mathrm{g}\right)+6\mathrm{NaOH}\left(\mathrm{aq}\right)\stackrel{}{\to }5\mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{NaClO}}_3\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

(B) Washing soda with chlorine

Washing soda does not react with chlorine.

(C) Baking soda with chlorine

Baking soda does not react with chlorine.

Therefore slaked lime reacting with chlorine produces bleaching powder.

Hence, the correct option is (D).