Calculate the standard cell potential for each reaction below, and note whether the reaction is spontaneous under standard state conditions.
(a) Mg(s) + Ni2+ (aq) Mg2+ (aq) + Ni(3)
(b) 2Ag+ (aq) + Cu(s) Cu2+ (aq) + 2Ag(s)
(c) Mn(s) + Sn(NO3)2(aq) Mn(NO3)2 (aq) + Sn(s)
(d) 3Fe(NO3)2(aq) + Au(NO3)3(aq) 3Fe(NO3)3(aq) + Au(s)