In each of the following balanced oxidation-reduction equations, identify those elements that undergo changes in oxidation number and indicate the magnitude of the change in each case.
(a) I2O5(s) + 5 CO(g) → I2(s) + 5 CO2(g)
(b) 2 Hg2+(aq) + N2H4 (aq) → 2 Hg(l) + N2(g) + 4 H+(aq)
(c) 3 H2S(aq) + 2 H+(aq) + 2 NO3 - (aq) → 3 S(s) + 2 NO(g) + 4 H2O(l)
(d) Ba2+(aq) + 2 OH- (aq) + H2O2(aq) + 2 ClO2(aq) → Ba(ClO2)2 (s) + 2 H2O(l) + O2(g)