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.

What kind of compound can be added to the bleaching powder to obtain chlorine.

Answer 1

Chlorine is liberated when manganese oxide, lead oxide, and red lead react with conc $\mathrm{HCl}$, by oxidising $\mathrm{HCl}$. This oxidization is due to the metals which are less electronegative than chlorine. This oxidization is done by air to liberate the chlorine gas.

Bleaching Powder:

• Calcium hypochlorite is the chemical name of bleaching powder which exists in pale yellowish color with a very strong chlorine smell.
• The chemical formula is ${\mathrm{CaOCl}}_2$
• To obtain chlorine from bleaching powder, we can add a dilute acid like dilute hydrochloric acid and dilute sulphuric acid.

The reaction is as follows:

$CaOC{l}_2\left(s\right)+2HCl\left(aq\right)\to CaC{l}_2\left(s\right)+H_{2}O\left(l\right)+C{l}_2\left(g\right)$

Hence by the addition of dil $\mathrm{HCl}$, calcium chloride is formed liberating chlorine gas.