Question

Aqueous solutions of HgCl$_2$ and SnCl$_2$ cannot co-exist, why?

Hint:

Whenever an oxidizing salt (HgCl$_2$) and a reducing salt (SnCl$_2$) are mixed in aqueous medium, a redox reaction occurs, preventing their coexistence.

Answer 1

Aqueous solutions of HgCl$_2$ and SnCl$_2$ cannot co-exist because a redox reaction takes place between them.
- HgCl$_2$ (mercuric chloride) acts as an oxidizing agent.
- SnCl$_2$ (stannous chloride) acts as a reducing agent.
\[ HgCl_2 + SnCl_2 \;\longrightarrow\; Hg_2Cl_2 \downarrow + SnCl_4 \]
Here, Hg$^{2+}$ in HgCl$_2$ is reduced to Hg$^{+}$ (in Hg$_2$Cl$_2), while Sn$^{2+}$ in SnCl$_2$ is oxidized to Sn$^{4+}$.
Hence, they cannot remain together in the same solution.