In Hg₂Cl₂ + Cl₂ → 2HgCl₂, what is the change in oxidation number of mercury?
Hg (+1 in Hg₂Cl₂) becomes +2 in HgCl₂. Change = +2 - (+1) = +1.
Ref: NCERT Class 11 Chemistry > Chapter 7: Redox Reactions > Topic: Balancing Redox Reactions - Oxidation Number Method and Half Reaction