HardChemistryHigh School (11–12)Chemical Thermodynamics › Entropy, Gibbs Energy and SpontaneityNumerical

For N₂O₄(g) ⇌ 2NO₂(g), Δ H° = +57.2 kJ/mol and Δ S° = +175.8 J/(K mol).

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For $\text{N}_2\text{O}_4(g) \rightleftharpoons 2\text{NO}_2(g)$ , $\Delta H^\circ = +57.2\ \text{kJ/mol}$ and $\Delta S^\circ = +175.8\ \text{J/(K mol)}$ . Find $\Delta G^\circ$ and $K$ at $298\ \text{K}$ and at $350\ \text{K}$ . What does heating do to the equilibrium?

Need a reminder? The key ideaShow

At equilibrium $\Delta G = 0$ and $\Delta G^\circ = -RT\ln K = -2.303\,RT\log K$ , with $R = 8.314\ \text{J/(K mol)}$ and $\Delta G^\circ$ in J/mol. A negative $\Delta G^\circ$ gives $K > 1$ , a positive one $K < 1$ . At another temperature, find $\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$ first.

The worked solution

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For N₂O₄(g) ⇌ 2NO₂(g), Δ H° = +57.2 kJ/mol and Δ S° = +175.8 J/(K mol).

The worked solution

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