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Electrochemistry

Question
CBSEENCH12006016

Calculate the cell e.m.f. at 25° C for the following cell:
Mg(s) | Mg2+ (0.01 M) || Sn2+ (0.1 M) | Sn (s)
[Given E°Mg2+/Mg = – 2.34 V, E°Sn2+/Sn = – 0.136V, 1 F = 96,500 C mol–1]
Calculate the maximum work that can be accomplished by the operation of this cell.

Solution

Mg(s) | Mg2+ (0.01 M) || Sn2+ (0.1 M) | Sn(s)
Mg(s) → Mg2+ (aq) + 2e
(oxidation at anode)
Sn2+(aq) + 2e → Sn(s)
(reduction at cathode)

Net cell reaction Mg(s) +Sn2+(aq)Mg2+(aq)+SnEcell =ESn2+Sn0 -EMg2+Mg0= -0.136V -(-2.34V)= + 2.204VEcell = Ecell0 -0.05912log [Mg2+][Sn2+]=2.204V -0.05912log 0.010.1=2.204V- 0.05912log10-1Ecell =2.204V+ 0.05912Ecell =2.204V+0.0295Ecell= 2.2355VG =-nE°F= -2×2.2335V×96500=-431065.5j=-431.0655KJMaximum work done -G=+431.0655KJ