Question

Write the complete chemical equation for the following:

An excess of SnCl₂ solution is added to a solution of mercury (II) chloride.

Answer 1

When excess stannous chloride (SnCl₂) is added to a solution of mercury(II) chloride (HgCl₂), it reduces Hg²⁺ to metallic mercury (Hg) through an intermediate formation of mercurous chloride (Hg₂Cl₂) (a white precipitate).

\[\ce{HgCl2 + SnCl2 -> \underset{(white ppt)}{Hg2Cl2} + SnCl4}\]

\[\ce{HgCl2 + SnCl2 -> \underset{(black)}{2Hg} + SnCl4}\]

Overall net reaction is:

\[\ce{2HgCl2 + SnCl2 -> \underset{(black ppt)}{2Hg} + Cl2}\]