Predict whether the following reactions will be spontaneous in acidic solution under standard conditions.
a) Oxidation of Sn to Sn2+ by I2 (to form I-)
b) Reduction of Ni2+ to Ni by I-(to form I2)
c) Reduction of Ce4+ to Ce3+ by H2O2
d) Reduction of Cu2+ to Cu by Sn2+ (to form Sn4+)