Write the Nernst equation and emf of the following cells at 298 K:
(i) Mg(s)|Mg+2(0.001 M)∥Cu+2(0.0001 M)|Cu(s).
(ii) Fe(s)|Fe+2(0.001 M)∥H+(1M)|H2(g)(1bar)|Pt(s)
(iii) Sn(s)|Sn2+(0.050 M)∥H+(0.020 M)|H2(g)(1bar)|Pt(s)
(iv) Pt(s)|Br2(l)|Br−(0.010 M)∥H+(0.030 M)|H2(g)(1bar)|Pt(s).
(i) Eo=0.34−(−2.37)=2.71 V
E=E0−0.059nlog[Mg2+][Cu2+]
E=2.71−0.0592log0.001(0.0001)
E=2.6805 V
(ii) Eo=0−(−0.44)=0.44 V
E=E0−0.059nlog[Fe2+][H+]2
E=0.44−0.0592log0.001(1)2
E=0.5285 V
(iii) Eo=0−(−0.14)=0.14 V
E=E0−0.059nlog[Sn2+][H+]2
E=0.14−0.0592log0.050(0.020)2
E=0.08 V
(iv) Eo=0−1.08=−1.08 V
E=E0−0.0592log1[Br−]2[H+]2
E=−1.08−0.0592log1(0.01)2(0.030)2
E=−1.288 V