Tin(II) chloride (SnCl2) reacts with mercury(II) chloride (HgCl2) to form mercury(I) chloride (Hg2Cl2) and tin(IV) chloride (SnCl4). The reaction can be represented as follows:

SnCl2 + 2HgCl2 → Hg2Cl2 + SnCl4

In this reaction, tin(II) chloride is oxidized from a +2 oxidation state to a +4 oxidation state, while mercury(II) chloride is reduced from a +2 oxidation state to a +1 oxidation state. The reaction is a redox reaction, involving the transfer of electrons from tin(II) to mercury(II).