---
title: "A rigid, sealed vessel contains an equilibrium mixture of \\(\\text{N}_2\\text{O}_4(g)\\) and \\(\\text{NO}_2(g)\\) at \\(298 \\, \\text{K}\\) according to the reaction represented below.  \\[ \\text{N}_2\\text{O}_4(g) \\rightleftharpoons 2\\,\\text{NO}_2(g) \\qquad \\Delta H^\\circ_{\\text{rxn}} = +57.2 \\, \\text{kJ/mol}_{\\text{rxn}} \\]  The temperature of the vessel is increased from \\(298 \\, \\text{K}\\) to \\(350 \\, \\text{K}\\). Which of the following correctly predicts and explains the change in the equilibrium partial pressure of \\(\\text{NO}_2(g)\\) after equilibrium is re-established?"
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url: "https://nerd-notes.com/ubq/119722/"
date_modified: "2026-08-21T17:12:08+00:00"
---

# A rigid, sealed vessel contains an equilibrium mixture of \(\text{N}_2\text{O}_4(g)\) and \(\text{NO}_2(g)\) at \(298 \, \text{K}\) according to the reaction represented below.

\[
\text{N}_2\text{O}_4(g) \rightleftharpoons 2\,\text{NO}_2(g)
\qquad \Delta H^\circ_{\text{rxn}} = +57.2 \, \text{kJ/mol}_{\text{rxn}}
\]

The temperature of the vessel is increased from \(298 \, \text{K}\) to \(350 \, \text{K}\). Which of the following correctly predicts and explains the change in the equilibrium partial pressure of \(\text{NO}_2(g)\) after equilibrium is re-established?

A rigid, sealed vessel contains an equilibrium mixture of \(\text{N}_2\text{O}_4(g)\) and \(\text{NO}_2(g)\) at \(298 \, \text{K}\) according to the reaction represented below.

\[
\text{N}_2\text{O}_4(g) \rightleftharpoons 2\,\text{NO}_2(g)
\qquad \Delta H^\circ_{\text{rxn}} = +57.2 \, \text{kJ/mol}_{\text{rxn}}
\]

The temperature of the vessel is increased from \(298 \, \text{K}\) to \(350 \, \text{K}\). Which of the following correctly predicts and explains the change in the equilibrium partial pressure of \(\text{NO}_2(g)\) after equilibrium is re-established?

- **A.** The partial pressure of \(\text{NO}_2(g)\) decreases because the increased temperature raises the total pressure inside the rigid vessel, which shifts the equilibrium toward the side with fewer moles of gas.
- **B.** The partial pressure of \(\text{NO}_2(g)\) decreases because adding thermal energy shifts an endothermic reaction toward the reactant side to dissipate the added heat, lowering \(K_p\).
- **C.** The partial pressure of \(\text{NO}_2(g)\) increases because the increase in temperature decreases the value of \(K_p\), which causes \(Q_p > K_p\) and drives the forward reaction.
- **D.** The partial pressure of \(\text{NO}_2(g)\) increases because the value of \(K_p\) increases for an endothermic reaction, resulting in \(Q_p < K_p\) immediately after the temperature increase.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119722/*