Question

Assume we know the Gibbs free energy of reaction for a chemical reaction taking place at 298 K. What additional thermodynamic information do we need to know to compute the equilibrium constant of the reaction (a) at 298 K and (b) at 350 K? (You may assume that no phase transitions take place in this temperature range.)

Answer 1

The relationship between Gibbs free energy change and reaction quotient is given as:

∆G = ∆G° + RT ln Q

Q is the reaction quotient and it is the state of the system other than the equilibrium state. When Q is equal to equilibrium constant K then free energy change ∆G = 0

So, at equilibrium the above equation becomes

0 = ∆G° + RT ln K

∆G° = - RT ln K

This means if we have the value of standard free energy change then we need only gas constant (R) value and temperature .R = 8.314 J K^-1mol^-1

For a) T = 298 K

For b) T = 350 K