---
title: "A mixture of \\(\\text{PCl}_5\\text{(g)}\\), \\(\\text{PCl}_3\\text{(g)}\\), and \\(\\text{Cl}_2\\text{(g)}\\) is initially at equilibrium inside a cylinder fitted with a movable piston, as represented by the following equation:  \\[ \\text{PCl}_5\\text{(g)} \\rightleftharpoons \\text{PCl}_3\\text{(g)} + \\text{Cl}_2\\text{(g)} \\quad \\Delta H^\\circ = +88 \\text{ kJ/mol}_{rxn} \\]  The volume of the cylinder is decreased by compressing the gas mixture, and the temperature of the system is simultaneously increased. Which of the following correctly predicts the effect of the temperature increase on the equilibrium constant, \\(K_p\\), and describes the initial shift caused by the decrease in volume alone?"
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url: "https://nerd-notes.com/ubq/121506/"
date_modified: "2026-08-23T05:04:54+00:00"
---

# A mixture of \(\text{PCl}_5\text{(g)}\), \(\text{PCl}_3\text{(g)}\), and \(\text{Cl}_2\text{(g)}\) is initially at equilibrium inside a cylinder fitted with a movable piston, as represented by the following equation:

\[ \text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)} \quad \Delta H^\circ = +88 \text{ kJ/mol}_{rxn} \]

The volume of the cylinder is decreased by compressing the gas mixture, and the temperature of the system is simultaneously increased. Which of the following correctly predicts the effect of the temperature increase on the equilibrium constant, \(K_p\), and describes the initial shift caused by the decrease in volume alone?

A mixture of \(\text{PCl}_5\text{(g)}\), \(\text{PCl}_3\text{(g)}\), and \(\text{Cl}_2\text{(g)}\) is initially at equilibrium inside a cylinder fitted with a movable piston, as represented by the following equation:

\[ \text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)} \quad \Delta H^\circ = +88 \text{ kJ/mol}_{rxn} \]

The volume of the cylinder is decreased by compressing the gas mixture, and the temperature of the system is simultaneously increased. Which of the following correctly predicts the effect of the temperature increase on the equilibrium constant, \(K_p\), and describes the initial shift caused by the decrease in volume alone?

- **A.** \(K_p\) increases, and the decrease in volume causes \(Q_p < K_p\), favoring a shift toward the products.
- **B.** \(K_p\) decreases, and the decrease in volume causes \(Q_p > K_p\), favoring a shift toward the reactants.
- **C.** \(K_p\) increases, and the decrease in volume causes \(Q_p > K_p\), favoring a shift toward the reactants.
- **D.** \(K_p\) decreases, and the decrease in volume causes \(Q_p < K_p\), favoring a shift toward the products.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121506/*