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Question

For the reaction 2Fe3+(aq)+2I(aq)2Fe2+(aq)+I2(s)
The magnitude of the standard molar free energy change,
ΔrG0m=______kJ (Round off the Nearest Integer).
E0Fe2+/Fe(s)=0.440 VE0Fe3+/Fe(s)=0.036 VE0I2/2I=0.539 VF=96500 C

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Solution

Answer: 45 kJ

2Fe3+(aq)+2I(aq)2Fe+2(aq)+I2(s)

ΔG0=nFE0

Fe3+(aq)+eFe2+(aq)....(1); ΔG01=1FE0
Fe2+(aq)+2eFe(s)......(2); ΔG02=+2F×0.44

Adding equation (1) and (2), we get,
Fe3+(aq)+3eFe(s).......(3); ΔG03=3FE0
Thus,
ΔG03=ΔG01+ΔG02
3F×0.036=1FE0+2F×0.44

E0Fe+3/Fe+2=3×(0.036)2×(0.44)
E0Fe+3/Fe+2=3×(0.036)+2×(0.44)

=0.108+0.88

=0.772 V

E0 of the given reaction is
Eocell=EoFe+3/Fe+2+EoI/I2

=0.7720.539=0.233V

ΔG°=nFE0cell

=2×96500×0.233

=44969 J=44.9 kJ45 kJ
Thus, answer is 45

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