Chemistry B
Mrs. Frost
Oxidation-Reduction Homework Packet
12. Use the changes in oxidation numbers to identify which atoms are oxidized and which are reduced in each reaction.
A.
$$2{\mathrm{Na}}_{(s)}+{\mathrm{Cl}}_{2(g)}\to 2{\mathrm{NaCl}}_{(s)}$$
Oxidized
Reduced
B.
$$2{\mathrm{HNO}}_{3(aq)}+6{\mathrm{HI}}_{(aq)}\to 2{\mathrm{NO}}_{(g)}+3{\mathrm{I}}_{2(s)}+4{\mathrm{H}}_2{\mathrm{O}}_{(\ell )}$$
Oxidized Reduced
C.
$$3{\mathrm{H}}_2{\mathrm{S}}_{(g)}+2{\mathrm{HNO}}_{3(aq)}\to 3{\mathrm{S}}_{(s)}+2{\mathrm{NO}}_{(g)}+4{\mathrm{H}}_2{\mathrm{O}}_{(\hslash )}$$
Oxidized Reduced
D.
$$2{\mathrm{PbSO}}_{4(s)}+2{\mathrm{H}}_2{\mathrm{O}}_{(l)}\to {\mathrm{Pb}}_{(s)}+{\mathrm{PbO}}_{2(s)}+2{\mathrm{H}}_2{\mathrm{SO}}_{4(aq)}$$
Oxidized Reduced
13. For each reaction in Problem $\mathrm{\#}$, identify the reducing agent and the oxidizing agent.
A.
$$2{\mathrm{Na}}_{(s)}+{\mathrm{Cl}}_{2(g)}\to 2{\mathrm{NaCl}}_{(s)}$$
Oxidizing Agent Reducing Agent
B.
$$2{\mathrm{HNO}}_{3(aq)}+6{\mathrm{HI}}_{(aq)}\to 2{\mathrm{NO}}_{(g)}+3{\mathrm{I}}_{2(s)}+4{\mathrm{H}}_2{\mathrm{O}}_{(l)}$$
Oxidizing Agent Reducing Agent
C.
$$3{\mathrm{H}}_2{\mathrm{S}}_{(g)}+2{\mathrm{HNO}}_{3(aq)}\to 3{\mathrm{S}}_{(s)}+2{\mathrm{NO}}_{(g)}+4{\mathrm{H}}_2{\mathrm{O}}_{(t)}$$
Oxidizing Agent Reducing Agent
D.
$$2{\mathrm{PbSO}}_{4(s)}+2{\mathrm{H}}_2{\mathrm{O}}_{(\hslash )}\to {\mathrm{Pb}}_{(s)}+{\mathrm{PbO}}_{2(s)}+2{\mathrm{H}}_2{\mathrm{SO}}_{4(aq)}$$
Oxidizing Agent Reducing Agent

Step 1 ：First, we need to find the oxidation numbers of each element in the reactants and products.

Step 2 ：For reaction A: $2{\mathrm{Na}}_{(s)}+{\mathrm{Cl}}_{2(g)}\to 2{\mathrm{NaCl}}_{(s)}$, the oxidation numbers are: Na: 0 to +1, Cl: 0 to -1. So, Na is oxidized and Cl is reduced.

Step 3 ：For reaction B: $2{\mathrm{HNO}}_{3(aq)}+6{\mathrm{HI}}_{(aq)}\to 2{\mathrm{NO}}_{(g)}+3{\mathrm{I}}_{2(s)}+4{\mathrm{H}}_2{\mathrm{O}}_{(\ell )}$, the oxidation numbers are: N: +5 to +2, I: -1 to 0, H: +1 (no change), O: -2 (no change). So, N is reduced and I is oxidized.

Step 4 ：For reaction C: $3{\mathrm{H}}_2{\mathrm{S}}_{(g)}+2{\mathrm{HNO}}_{3(aq)}\to 3{\mathrm{S}}_{(s)}+2{\mathrm{NO}}_{(g)}+4{\mathrm{H}}_2{\mathrm{O}}_{(\hslash )}$, the oxidation numbers are: S: -2 to 0, N: +5 to +2, H: +1 (no change), O: -2 (no change). So, S is oxidized and N is reduced.

Step 5 ：For reaction D: $2{\mathrm{PbSO}}_{4(s)}+2{\mathrm{H}}_2{\mathrm{O}}_{(\hslash )}\to {\mathrm{Pb}}_{(s)}+{\mathrm{PbO}}_{2(s)}+2{\mathrm{H}}_2{\mathrm{SO}}_{4(aq)}$, the oxidation numbers are: Pb: +2 to 0 and +4, S: +6 (no change), O: -2 (no change), H: +1 (no change). So, Pb is both oxidized and reduced.

Step 6 ：Next, we identify the reducing and oxidizing agents for each reaction.

Step 7 ：For reaction A: Oxidizing Agent: ${\mathrm{Cl}}_2$, Reducing Agent: $\mathrm{Na}$

Step 8 ：For reaction B: Oxidizing Agent: ${\mathrm{HNO}}_3$, Reducing Agent: $\mathrm{HI}$

Step 9 ：For reaction C: Oxidizing Agent: ${\mathrm{HNO}}_3$, Reducing Agent: ${\mathrm{H}}_2\mathrm{S}$

Step 10 ：For reaction D: Oxidizing Agent: ${\mathrm{PbSO}}_4$, Reducing Agent: ${\mathrm{PbSO}}_4$