## The reaction of cr2+(aq) with cr2o2−7(aq) in acid solution to form cr3+(aq). calculate δg∘rxn.

Question

The reaction of cr2+(aq) with cr2o2−7(aq) in acid solution to form cr3+(aq). calculate δg∘rxn.

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1. The reaction is:
6 Cru00b2u207a + Cru2082Ou2087u00b2u207b + 14 Hu207au2192 8 Cru00b3u207a + 7 Hu2082O

Eu2080 = 1.33 – (-0.5) = 1.83 V

u0394G = – n f Eu2080
= – 6 * 96485 * 1.83
= – 1059405.3 J / mol
= – 1059.4 kJ / mol

The correct answer is -1059.45 kJ.

Explanation:

The balanced equation is:

6Cru2082u207a + Cru2082Ou2087u00b2u207b + 14Hu207a u21d2 8Cru2083u207a + 7Hu2082O

In the mentioned reaction 6 electrons are transferred

By calculating Ecell with the use of reduction potential of each cell:

Ecell = Eox + Ered

Ered = 0.50V

Eox = -Ered = -(-0.50V) = 0.50V

Ered = 1.33V

Ecell = 0.50V + 1.33V

Ecell = 1.83V

Now in order to calculate u0394G

n = 6, Faraday constant (f) = 9.68470 x 10u2074 = 96847 C molu207bu00b9

u0394G = -nFE

u0394G = -6 x 96487 C mol-1 x 1.83V

u0394G = -1059.42 KJ

The relation between u0394G and u0394Gu00b0rxn

u0394G = u0394Gu00b0 + RTlnQ

Under the standard condition Q = 1 and u0394G = u0394Gu00b0

Thus,

u0394Gu00b0rxn = u0394G = -1059.42 KJ