Question

Manganese $\left(IV\right)$ oxide, lead $\left(IV\right)$ oxide and red lead $\left(P{b}_3{O}_4\right)$ react with concentrated hydrochloric acid liberating chlorine.

(i) What is the common property shown by these metal oxides?

(ii) Write the equation for the reaction of hydrochloric acid with $\left(P{b}_3{O}_4\right)$?

(iii) What kind of compound can be added to the bleaching powder to obtain chlorine?

Answer 1

1. Manganese oxide, Lead oxide, and Red lead are far less electronegative than Chlorine, they can oxidize $\mathrm{HCl}$ and liberate Chlorine.

$\mathrm{HCl}$ is oxidized catalytically by air to generate elemental Chlorine gas. Because $F$, $O$, and $N$ have a higher electronegative charge, they do not react with $\mathrm{HCl}$.

2. The following is a representation of the reaction with concentrated hydrochloric acid;

${\mathrm{Pb}}_3{\mathrm{O}}_4\left(\mathrm{s}\right)+8\mathrm{HCl}\left(\mathrm{aq}\right)\to 3{\mathrm{PbCl}}_2\left(\mathrm{aq}\right)+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)$

3. When $HCl$ reacts with bleaching powder, it produces Calcium Chloride $(CaC{l}_2)$, Chlorine $\left(C{l}_2\right)$, and water, hence a weak acid (diluted Hydrochloric acid) can be used to acquire chlorine.

$CaOC{l}_2+HCl\to CaC{l}_2+C{l}_2+H_{2}O$