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1)Calculate the free energy %u0394G (in kJ/mol) for a reaction 4A + 3 B %u21CC 1

ID: 783691 • Letter: 1

Question

1)Calculate the free energy %u0394G (in kJ/mol) for a reaction   4A + 3 B   %u21CC 1 C + 3 D

knowing that the concentrations are: [A] = 0.78 M,   [B] = 1.49 M,   [C] = 0.5 M,   [D] = 1.38 M.

The standard free energy and the temperature of the reaction are respectively

DeltaG=?

2)Calculate the free energy %u0394G (in kJ/mol) for a reaction   4A + 1 B   %u21CC 2 C + 2 D

knowing that the concentrations are: [A] = 0.43 M,   [B] = 1.04 M,   [C] = 1.64 M,   [D] = 1.19 M.

The equilibrium constant, Kc , is 6.42e+1 , and T = -17 degree C.


DeltaG=?

Explanation / Answer

(A) %u0394G = %u0394G0 + RT ln C^c . D^d/A^a.B^b


where R = 8.3 J mol-1 K-1 and T = 248 Kelvin


= 95.3 + 8.3*248*ln(1.073)


= 95.3 + 8.3*248*0.07


= 239.38 Kj/mol


(B) At equilibrium, DeltaG = 0 and Q = K


But DeltaG = DeltaG0 + RT ln Q


Hence DeltaG0 = - RT ln K


= -8.314*256*ln 6.42e+1


=-3937.5 Kj/mol


So, %u0394G = -3937.5 + 8.314*256*ln(107.12) [ applying the same formula as above]


= -3937.5+ 9939.5


= 6002.05 kj/mol