What is the change in oxidation number of sulfur in the reaction 2H₂S + O₂ → 2S + 2H₂O?
S (-2 in H₂S) becomes 0 in S. Change = 0 - (-2) = +2.
Ref: NCERT Class 11 Chemistry > Chapter 7: Redox Reactions > Topic: Balancing Redox Reactions - Oxidation Number Method and Half Reaction