---
title: "A mixture of \\(\\text{X}_2\\text{(g)}\\), \\(\\text{Y}_2\\text{(g)}\\), and \\(\\text{XY}\\text{(g)}\\) is placed in a rigid \\(1.0\\text{ L}\\) container and allowed to reach chemical equilibrium at a temperature of \\(T_1 = 500\\text{ K}\\), as represented in the diagram.  \\[ \\text{X}_2\\text{(g)} + \\text{Y}_2\\text{(g)} \\rightleftharpoons 2\\,\\text{XY}\\text{(g)} \\quad \\Delta H^\\circ = -85\\text{ kJ/mol}_{\\text{rxn}} \\]  The temperature of the container is then decreased to \\(T_2 = 300\\text{ K}\\), and the system is allowed to establish a new equilibrium. Which of the following particulate diagrams best represents the system at the new equilibrium at \\(T_2\\)?"
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url: "https://nerd-notes.com/ubq/119851/"
date_modified: "2026-08-21T08:13:05+00:00"
---

# A mixture of \(\text{X}_2\text{(g)}\), \(\text{Y}_2\text{(g)}\), and \(\text{XY}\text{(g)}\) is placed in a rigid \(1.0\text{ L}\) container and allowed to reach chemical equilibrium at a temperature of \(T_1 = 500\text{ K}\), as represented in the diagram.

\[ \text{X}_2\text{(g)} + \text{Y}_2\text{(g)} \rightleftharpoons 2\,\text{XY}\text{(g)} \quad \Delta H^\circ = -85\text{ kJ/mol}_{\text{rxn}} \]

The temperature of the container is then decreased to \(T_2 = 300\text{ K}\), and the system is allowed to establish a new equilibrium. Which of the following particulate diagrams best represents the system at the new equilibrium at \(T_2\)?

A mixture of \(\text{X}_2\text{(g)}\), \(\text{Y}_2\text{(g)}\), and \(\text{XY}\text{(g)}\) is placed in a rigid \(1.0\text{ L}\) container and allowed to reach chemical equilibrium at a temperature of \(T_1 = 500\text{ K}\), as represented in the diagram.

\[ \text{X}_2\text{(g)} + \text{Y}_2\text{(g)} \rightleftharpoons 2\,\text{XY}\text{(g)} \quad \Delta H^\circ = -85\text{ kJ/mol}_{\text{rxn}} \]

The temperature of the container is then decreased to \(T_2 = 300\text{ K}\), and the system is allowed to establish a new equilibrium. Which of the following particulate diagrams best represents the system at the new equilibrium at \(T_2\)?

![A legend maps: open circle = X atom, solid black circle = Y atom. Inside a square border representing a rigid container, the following gas-phase particles are evenly distributed: exactly 2 homonuclear diatomic molecules of \(\text{X}_2\) (each composed of 2 bonded open circles), exactly 2 homonuclear diatomic molecules of \(\text{Y}_2\) (each composed of 2 bonded solid black circles), and exactly 4 heteronuclear diatomic molecules of \(\text{XY}\) (each composed of 1 open circle bonded to 1 solid black circle). No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787299983-nLqdfX.jpg)

- **A.** Diagram A
- **B.** Diagram B
- **C.** Diagram C
- **D.** Diagram D

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119851/*