Question

What is the significance of the Gibbs-Helmholtz Equation in chemical thermodynamics?

• A. It predicts the direction of chemical reactions.
• B. It relates the Gibbs free energy change to temperature and enthalpy change.
• C. It calculates the equilibrium constant at different pressures.
• D. It determines the molecular weights of gases.

Hint:

Gibbs-Helmholtz Equation. Relates the change in Gibbs free energy (\(\Delta G\)) with temperature to the enthalpy change (\(\Delta H\)) of the process. Used to determine how spontaneity (\(\Delta G\)) and equilibrium constants change with temperature.

Answer 1

The Correct Option is B

The Gibbs-Helmholtz equation describes the temperature dependence of the Gibbs free energy (\(G\)) or the Gibbs free energy change (\(\Delta G\)) of a system or process.
One common form is: $$ \left( \frac{\partial (\Delta G / T)}{\partial T} \right)_P = -\frac{\Delta H}{T^2} $$ Another form relates the change in \(\Delta G\) with temperature directly to the enthalpy change (\(\Delta H\)): $$ \Delta G = \Delta H + T \left( \frac{\partial (\Delta G)}{\partial T} \right)_P $$ These equations show how \(\Delta G\) varies with temperature, connecting it explicitly to the enthalpy change (\(\Delta H\)) of the process.
While \(\Delta G\) itself predicts reaction direction (spontaneity) (Option 1), and its relation to the equilibrium constant \(K\) (\(\Delta G^\circ = -RT \ln K\)) allows calculation of K (partly related to Option 3, via temperature), the *specific significance* of the Gibbs-Helmholtz equation is its description of the *temperature dependence* of \(\Delta G\) and its direct link to \(\Delta H\).
Option (2) best captures this significance.
Option (4) is incorrect.