Question

In the redox reaction below, which is the reducing agent? MnO2 (s) + 4H+(aq) + 2Clmc007-1.jpg (aq) mc007-2.jpg Mn2+(aq) + 2H2O(l) + Cl2(g)

Answer 1

Answer is:
Redox reaction: MnO₂ + 4H⁺ + 2Cl⁻ → Mn²⁺ + 2H₂O + Cl₂.
Cl⁻ lost one electron (two Cl⁻ lost two electrons) and change oxidation number to zero, so Cl⁻ is reducing reagent. 
Mn change oxidation number from + 4 to +2, Mn is oxidizing reagent.
Hydrogen don't change oxidation number.

Answer 2

The answer is Cl- or A. Hope it helps