Question

A sample of bleaching powder was kept in an air tight container. After a month, it lost some of its chlorine content. How will you account for it ?

Answer 1

1. Bleaching powder also called calcium oxychloride $\left({\mathrm{CaOCl}}_2\right)$ is a oxidizing agent.
2. When the bleaching powder $\left({\mathrm{CaOCl}}_2\right)$ is kept in an air-tight container, it decomposes slowly on its own forming calcium chlorate $\left(\mathrm{Ca}{\left({\mathrm{ClO}}_3\right)}_2\right)$ and calcium chloride $\left({\mathrm{CaCl}}_2\right)$ and this reaction is called auto-oxidation.

Chemical formula:

$6[{\mathrm{CaOCl}}_2·{\mathrm{H}}_2\mathrm{O}]\left(\mathrm{aq}\right)\stackrel{}{\to }\mathrm{Ca}{\left({\mathrm{ClO}}_3\right)}_2\left(\mathrm{s}\right)+5{\mathrm{CaCl}}_2\left(\mathrm{s}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, this reaction results decrease in chlorine contents.