A) \[Cu+2A{{g}^{+}}(aq)\to C{{u}^{2+}}(aq)+2Ag\]
B) \[Zn+2A{{g}^{+}}(aq)\to Z{{n}^{2+}}(aq)+2Ag\]
C) \[{{H}_{2}}+N{{i}^{2+}}(aq)\to 2{{H}^{+}}(aq)+Ni\]
D) \[Zn+C{{u}^{2+}}(aq)\to Z{{n}^{2+}}(aq)+Cu\]
E) \[Zn+2{{H}^{+}}(aq)\to Z{{n}^{2+}}(aq)+{{H}_{2}}\]
Correct Answer: B
Solution :
Standard oxidation potentials of Zn, Cu, Ag and Ni electrode are\[+\text{ }0.76,-0.34,-0.80\]and +0.25 V respectively. (Given) \[Z{{n}^{2+}}+2{{e}^{-}}\to Zn,\] \[{{E}_{cell}}=-0.76\,V\] \[C{{u}^{2+}}+2{{e}^{-}}\to Cu,\] \[{{E}_{cell}}=+0.34\,V\] \[A{{g}^{+}}+{{e}^{-}}\to Ag,\] \[{{E}_{cell}}+0.80\,V\] \[N{{i}^{2+}}+2{{e}^{-}}\to Ni,\] \[{{E}_{cell}}=-0.25V\] (a) \[Cu+2A{{g}^{+}}(aq)\to C{{u}^{2+}}(aq)+2Ag\] \[E_{cell}^{o}=E_{cathode}^{o}-E_{anode}^{o}\] \[{{E}_{cell}}=0.80-0.34=0.46\,V\] (b) \[Zn+2A{{g}^{+}}(aq)\to Z{{n}^{2+}}(aq)+2Ag\] \[{{E}_{cell}}=0.80-(-0.76)=1.56\,V\] (maximum voltage) (c) \[{{H}_{2}}+N{{i}^{2+}}(aq)\to 2{{H}^{+}}(aq)+Ni\] \[{{E}_{cell}}=-0.25\,V\] (d) \[Zn+C{{u}^{2+}}(aq)\to Z{{n}^{2+}}(aq)+Cu\] \[{{E}_{cell}}=0.34-(-0.76)=1.00V\] (e) \[Zn+2{{H}^{+}}(aq)\to Z{{n}^{2+}}(aq)+{{H}_{2}}\] \[{{E}_{cell}}=0-(0.76\,V)=0.76\,V\]
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