Question

Calculate the equilibrium constant at 37 K for a reaction with ΔH_rxn^o = 10 kJ and ΔS_rxn^o = 100 J/K.

Calculate the equilibrium constant at 129 K for the thermodynamic data in the previous question.

Answer 1

1)

deltaH = 10.0KJ/mol

deltaS = 100J/mol.K= 0.1 KJ/mol.K

T = 37 K

we have below equation to be used:

deltaG = deltaH - T*deltaS

deltaG = 10.0 - 37.0 * 0.1

deltaG = 6.3 KJ/mol

deltaG = 6300 J/mol

we have below equation to be used:

deltaG = -R*T*ln Kc

6300 = - 8.314*37.0* ln(Kc)

ln Kc = -20.4799

Kc = 1.28*10^-9

Answer: 1.28*10^-9

2)

deltaH = 10.0KJ/mol

deltaS = 100J/mol.K

= 0.1 KJ/mol.K

T = 129 K

we have below equation to be used:

deltaG = deltaH - T*deltaS

deltaG = 10.0 - 129.0 * 0.1

deltaG = -2.9 KJ/mol = -2900 J/mol

we have below equation to be used:

deltaG = -R*T*ln Kc

-2900 = - 8.314*129.0* ln(Kc)

ln Kc = 2.7039

Kc = 14.9

Answer: 14.9