Section-D: Comprehension Type
Let ΔG° be the difference in free energy of the reaction when all the reactants and products are in the standard state (1 atmospheric pressure and 298K) and KC and KP be the thermodynamic equilibrium constant of the reaction. Both are related to each other at temperature T by the following relation:
ΔG° = –2.303 RT log KC
and ΔG° = –2.303 RT log Kp (incase of ideal gas)
This equation represents one of the most important results of thermodynamics and relates to the equilibrium constant of a reaction to a thermodynamic property.
It is sometimes easier to calculate the free energy in a reaction rather than to measure the equilibrium constant.
Standard free energy change can be thermodynamically calculated as
ΔG° = ΔH° –TΔS°
Here ΔH° = standard enthalpy change
ΔS° = standard entropy change.
H2(g) + I2(g) ⇌ 2HI(g) Calculate the value of ΔG° for the reaction at that temperature
At 490°C, the value of equilibrium constant; KP is 45.9 the reaction
H2(g) + I2(g) ⇌ 2HI(g)
Calculate the value of ΔG° for the reaction at that temperature