---
title: "The reversible reaction between nitrogen dioxide and dinitrogen tetroxide is represented by the following equation:  \\[ 2\\text{NO}_2\\text{(g)} \\rightleftharpoons \\text{N}_2\\text{O}_4\\text{(g)} \\]  A mixture of \\(\\text{NO}_2\\text{(g)}\\) and \\(\\text{N}_2\\text{O}_4\\text{(g)}\\) is initially at equilibrium inside a rigid cylinder fitted with a movable piston at a constant temperature (State 1). The piston is then pushed downward to reduce the volume to half its original value at the same temperature, resulting in the non-equilibrium mixture shown in State 2. Which of the following statements best explains how and why the system responds as it proceeds to establish a new equilibrium?"
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url: "https://nerd-notes.com/ubq/120318/"
date_modified: "2026-08-23T04:04:39+00:00"
---

# The reversible reaction between nitrogen dioxide and dinitrogen tetroxide is represented by the following equation:

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

A mixture of \(\text{NO}_2\text{(g)}\) and \(\text{N}_2\text{O}_4\text{(g)}\) is initially at equilibrium inside a rigid cylinder fitted with a movable piston at a constant temperature (State 1). The piston is then pushed downward to reduce the volume to half its original value at the same temperature, resulting in the non-equilibrium mixture shown in State 2. Which of the following statements best explains how and why the system responds as it proceeds to establish a new equilibrium?

The reversible reaction between nitrogen dioxide and dinitrogen tetroxide is represented by the following equation:

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

A mixture of \(\text{NO}_2\text{(g)}\) and \(\text{N}_2\text{O}_4\text{(g)}\) is initially at equilibrium inside a rigid cylinder fitted with a movable piston at a constant temperature (State 1). The piston is then pushed downward to reduce the volume to half its original value at the same temperature, resulting in the non-equilibrium mixture shown in State 2. Which of the following statements best explains how and why the system responds as it proceeds to establish a new equilibrium?

![A grayscale schematic shows two identical-width rectangular containers side-by-side with a top legend. The legend defines: one solid gray circle represents one \(\text{NO}_2\) molecule, and two conjoined solid black circles represent one \(\text{N}_2\text{O}_4\) molecule. The left container, labeled State 1 (Volume = \(V\)), has a piston at the top and contains exactly 4 separate solid gray circles and 2 conjoined solid black pairs evenly dispersed. The right container, labeled State 2 (Volume = \(V/2\)), has the piston lowered to half the initial height, containing the same 4 separate solid gray circles and 2 conjoined solid black pairs compressed into half the vertical space. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787457879-C4vMkO.jpg)

- **A.** The system will shift toward products because halving the volume causes \(Q < K\), meaning the rate of the forward reaction is greater than the rate of the reverse reaction.
- **B.** The system will shift toward products because decreasing the volume increases the value of \(K\), favoring the side of the reaction with fewer moles of gas.
- **C.** The system will shift toward reactants because halving the volume doubles all concentrations, causing \(Q > K\), which increases the rate of the reverse reaction.
- **D.** The system will not shift because the ratio of \(\text{NO}_2\text{(g)}\) molecules to \(\text{N}_2\text{O}_4\text{(g)}\) molecules in State 2 is identical to the ratio in State 1.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120318/*