4. By assigning oxidation numbers, identify the oxidising agent and the reducing agent
in each of the following reactions.
(a) 2Mg(s) + O2(g) → 2MgO(s)
(b) 2Na(s) + Br2(g) → 2NaBr(s)
(c) Br2 + 2KI → 2KBr + I2
(d) Fe2O3 + C → Fe + CO2
(e) 2NH3 + 3CuO → 3Cu + 3H2O + N2
5. The cell potential, or electromotive force (emf) is important because it is related to
the maximum electrical work that can be obtained from an electrochemical cell. A
voltaic cell is constructed that uses the following reaction and operates at 298K:
Zn(s) + Ni2+(aq) -> Zn2+(aq) + Ni(s)
Half reaction Standard Reduction Potential (Ered)
Ni2+(aq) + 2e- --> Ni(s) -0.280 V
Zn2+(aq) + 2e- --> Zn(s) -0.763 V
(a) What is the emf of this cell under standard conditions?