Q.
The cell potential (Ecell) of a reaction is related as ΔG=−nFEcell , where ΔG represents max. useful electrical work n = no. of moles of electrons exchanged during the reactionfor reversible cell reaction d(ΔG)=ΔrVdp−ΔrS⋅dTat constant pressure d(ΔG)=−ΔrS⋅dT ∵ At constant pressure ΔG=ΔH−T⋅ΔS . . . . (1)∴ ΔG=ΔH+Td(ΔG)dTp . . . . .(2)dEcell dTp is known as temperature coefficient of the e.m.f of the cell The temperature coefficient of the e.m.f. of cell, dEdT is given by : At 300K,ΔH for the reaction Zn(s)+AgCl(s)⟶ZnCl2(aq)+2Ag(s) is −218kJ/mol while the e.m.f. of the cell was 1.015V⋅dEdTp of the cell is: Calculate ΔS for the given cell reaction in Zn(s)+AgCl(s)⟶ZnCl2(aq)+2Ag(s) is −218kJ/mol while the e.m.f. of the cell was 1.015V⋅dEdTp of the cell is:
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a
nFΔS
b
ΔSnF
c
ΔSnFT
d
-nFE
e
−4.2×10−4VK−1
f
−3.81×10−4VK−1
g
0.11VK−1
h
7.62×10−4VK−1
i
-73.53 J/K mol
j
83.53 J/K mol
k
100 J/K mol
l
none of these
answer is , , .
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Detailed Solution
From equation 1 and 2,ΔS=−d(ΔG)dTΔS=d(nFE)dT⇒nFdEdT or dEdTp=ΔSnFFrom equation 2;ΔH=nFdEdTpT−nFEcell −218×1000=2×96500×300dEdTp-2 x 96500 x 1.015 dEdTp=−3.81×10−4 V K−1ΔS=nFdEdTp=2×96500×−3.81×10−4=−73.53J/mol−K
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