Sketch a voltaic cell for each redox reaction. Label the anode and cathode and indicate the half-reaction that occurs at each elec- trode and the species present in each solution. Also indicate the direction of electron flow. a. Ni2+(aq) + Mg(s) ¡ Ni(s) + Mg2+(aq) b. 2 H+ (aq) + Fe(s) ¡ H2(g) + Fe2+(aq) c. 2 NO3-(aq) + 8 H+(aq) + 3 Cu(s) ¡ 2 NO(g) + 4 H2O(l) + 3 Cu2+(aq