Identify the atoms that are oxidized and reduced, the change in oxidation state for each, and the oxidizing and reducing agents in each of the following equations: Mg(s) + NiCl_2(aq) rightarrow MgCl_2(aq) + Ni(s) PCl_3 + Cl_2(g) rightarrow PCl_5 (s) C_2H_4(g) + 3O_2(g) rightarrow 2CO_2(g) + 2H_2O(g) Zn(s) + H_2SO_4(aq) rightarrow ZnSO_4(aq) + H_2(g) 2K_2 S_2O_3(s) + I_2(s) rightarrow K_2S_4O_6(s) + 2KI(s) 3Cu(s) + 8HNO_2(aq) rightarrow 3 Cu(NO_3)_2(aq) + 2NO(g) + 4H_2O(l)