Question

The standard free energy change for a reaction can be calculated using the equation

where n is the number of electrons transferred F is Faraday\'s constant, 96.5 kJ ·molâ€"1 ·Vâ€"1 Î"E0\' is the change reduction potential

For each of the following reactions, determine the number of electrons transferred (n) and calculate standard free energy (Î"G0\').

a) half-reactions: fumarate2- + 2H+ <--> succinate2-
CoQH2 <--> CoQ + 2H+
overall reaction: fumarate2- + CoQH2 <--> succinate2- + CoQ Î"E0\' = -0.009V

n= Î"G0\' = kJ*mol-1

b) half-reactions: cytochrome c1(Fe2+) <--> cytochrome c1 (Fe3+)
cytochrome c (Fe3+) <--> cytochrome c (Fe2+)
overall reaction: cyt c1 (Fe2+) + cyt c (Fe3+) <--> cyt c1 (Fe3+) + cyt c (Fe2+) Î"E0\' = 0.02V
n= Î"G0\' = kJ*mol-1

Answer 1

a) 1,737 kJ

b) -1,93 kJ

Step-by-step explanation:

The standard free energy change (ΔG) can be determined using:

ΔG = -nFE

a) For the reaction:

Fumarate²⁻ + CoQH₂ ⇄ succinate²⁻ + CoQ

The transferred electrons are 2, As E=-0,009V:

ΔG = -2×96,5kJ/molV×-0,009V

ΔG = 1,737 kJ

b) For the reaction:

cytc1 (Fe²⁺) + cytc (Fe³⁺) ⇄ cytc1 (Fe³⁺) + cytc (Fe²⁺)

The transferred electron is n=1 and E=0,02V:

ΔG = -1×96,5kJ/molV×0,02V

ΔG = -1,93 kJ

I hope it helps!