---
title: "A sealed cylinder contains an equilibrium mixture represented by the equation  \\(2\\text{NO}_2\\text{(g)} \\rightleftharpoons \\text{N}_2\\text{O}_4\\text{(g)}\\)  At time \\(t_1\\), the volume of the cylinder is rapidly decreased to one-half its original value while the temperature remains constant. The concentrations are recorded in the graph.  Which statement best explains the concentration changes shown after \\(t_1\\)?"
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url: "https://nerd-notes.com/ubq/119509/"
date_modified: "2026-08-19T12:40:54+00:00"
---

# A sealed cylinder contains an equilibrium mixture represented by the equation

\(2\text{NO}_2\text{(g)} \rightleftharpoons \text{N}_2\text{O}_4\text{(g)}\)

At time \(t_1\), the volume of the cylinder is rapidly decreased to one-half its original value while the temperature remains constant. The concentrations are recorded in the graph.

Which statement best explains the concentration changes shown after \(t_1\)?

A sealed cylinder contains an equilibrium mixture represented by the equation

\(2\text{NO}_2\text{(g)} \rightleftharpoons \text{N}_2\text{O}_4\text{(g)}\)

At time \(t_1\), the volume of the cylinder is rapidly decreased to one-half its original value while the temperature remains constant. The concentrations are recorded in the graph.

Which statement best explains the concentration changes shown after \(t_1\)?

![Create a grayscale line graph with a bare white plotting area and no gridlines. Label the horizontal axis “Time” and the vertical axis “Concentration (M).” Put y-axis tick marks at 0.100, 0.150, 0.200, and 0.225, and place a thin vertical marker labeled t₁ near the middle. Include a legend mapping a solid curve to NO₂ and a dashed curve to N₂O₄. Before the marker, both curves coincide as a horizontal segment at 0.100. At the marker, each curve makes an instantaneous vertical jump to 0.200. After the marker, the solid curve smoothly decreases and levels off at 0.150, while the dashed curve smoothly increases and levels off at 0.225. Both approach their final plateaus over the same time interval with no oscillation. Use uniform black strokes, clear axis arrowheads, and compact textbook proportions. No other curves, labels, text, shading, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787143254-nKIjR3.jpg)

- **A.** The equilibrium shifts toward the reactants because decreasing the volume favors the side with the greater number of gas particles.
- **B.** The equilibrium does not shift after the initial jump because doubling both concentrations leaves \(Q\) equal to \(K\).
- **C.** The equilibrium shifts toward the products because decreasing the volume increases \(K\) at constant temperature.
- **D.** The equilibrium shifts toward the products because, for \(Q=\dfrac{[\text{N}_2\text{O}_4]}{[\text{NO}_2]^2}\), doubling both concentrations makes \(Q\) less than \(K\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119509/*