Question

Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:

1. $2AgBr (s) + C_6H_6O_2(aq) \rightarrow 2Ag(s) + 2HBr (aq) + C_6H_4O_2(aq)$
2. $HCHO(l) + 2[Ag (NH_3)_2] ^+ (aq) + 3OH^ - (aq) \rightarrow 2Ag(s) + HCOO ^- (aq) + 4NH_3(aq) + 2H_2O(l)$
3. $HCHO (l) + 2Cu^{ 2+}(aq) + 5 OH^ - (aq) \rightarrow Cu_2O(s) + HCOO ^- (aq) + 3H_2O(l)$
4. $N_2H_4(l) + 2H_2O_2(l) \rightarrow N_2(g) + 4H_2O(l)$
5. $Pb(s) + PbO_2(s) + 2H_2SO_4(aq) \rightarrow 2PbSO_4(s) + 2H_2O(l)$

Answer 1

(a)
Oxidised substance $\rightarrow$ $C_6H_6O_2$
Reduced substance $\rightarrow$ $AgBr$
Oxidising agent $\rightarrow$ $AgBr$
Reducing agent $\rightarrow$ $C_6H_6O_2$

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(b)
Oxidised substance $\rightarrow$ $HCHO$
Reduced substance $\rightarrow$ $[Ag(NH_3)_2]^+$
Oxidising agent $\rightarrow$ $[Ag(NH_3)_2]^+$
Reducing agent $\rightarrow$ $HCHO$

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(c)
Oxidised substance $\rightarrow$ $HCHO$
Reduced substance $\rightarrow$ $Cu ^{2+}$
Oxidising agent $\rightarrow$ $Cu ^{2+}$
Reducing agent $\rightarrow$ $HCHO$

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(d) Oxidised substance $\rightarrow$ $N_2H_4$
Reduced substance $\rightarrow$ $H_2O_2$
Oxidising agent $\rightarrow$ $H_2O_2$
Reducing agent $\rightarrow$ $N_2H_4$

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(e) Oxidised substance $\rightarrow$ $Pb$
Reduced substance $\rightarrow$ $PbO_2$
Oxidising agent $\rightarrow$ $PbO_2$
Reducing agent $\rightarrow$ $Pb$