---
title: "The reaction energy profile below represents two competing pathways for the conversion of reactant \\(\\text{R(g)}\\) into products \\(\\text{X(g)}\\) and \\(\\text{Y(g)}\\).  An experiment is conducted in which \\(\\text{R(g)}\\) is allowed to react at \\(200\\text{ K}\\), yielding predominantly \\(\\text{X(g)}\\). When the reaction is carried out at \\(500\\text{ K}\\) and given sufficient time to reach chemical equilibrium, \\(\\text{Y(g)}\\) is found to be the predominant product.  Which of the following statements is best supported by the diagram and the experimental observations?"
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url: "https://nerd-notes.com/ubq/123931/"
date_modified: "2026-09-28T12:32:18+00:00"
---

# The reaction energy profile below represents two competing pathways for the conversion of reactant \(\text{R(g)}\) into products \(\text{X(g)}\) and \(\text{Y(g)}\).

An experiment is conducted in which \(\text{R(g)}\) is allowed to react at \(200\text{ K}\), yielding predominantly \(\text{X(g)}\). When the reaction is carried out at \(500\text{ K}\) and given sufficient time to reach chemical equilibrium, \(\text{Y(g)}\) is found to be the predominant product.

Which of the following statements is best supported by the diagram and the experimental observations?

The reaction energy profile below represents two competing pathways for the conversion of reactant \(\text{R(g)}\) into products \(\text{X(g)}\) and \(\text{Y(g)}\).

An experiment is conducted in which \(\text{R(g)}\) is allowed to react at \(200\text{ K}\), yielding predominantly \(\text{X(g)}\). When the reaction is carried out at \(500\text{ K}\) and given sufficient time to reach chemical equilibrium, \(\text{Y(g)}\) is found to be the predominant product.

Which of the following statements is best supported by the diagram and the experimental observations?

![A grayscale reaction energy profile with a vertical axis labeled 'Gibbs Free Energy, \(G\)' and a horizontal axis labeled 'Reaction Coordinate'. Both axes have arrows indicating increasing direction; no gridlines appear. At the far left, a horizontal plateau represents the initial state labeled '\(\text{R}\)'. From '\(\text{R}\)', two smooth curves split into competing reaction pathways. The first curve, drawn with a dashed line, ascends to a lower peak labeled '\(\text{TS}_1\)' and descends to a horizontal plateau labeled '\(\text{X}\)' that lies below '\(\text{R}\)'. The second curve, drawn with a solid line, ascends to a higher peak labeled '\(\text{TS}_2\)' and descends to a horizontal plateau labeled '\(\text{Y}\)' that lies substantially lower than both '\(\text{R}\)' and '\(\text{X}\)'. A legend in the upper-right corner indicates: dashed line = Pathway to \(\text{X}\), solid line = Pathway to \(\text{Y}\). No other curves, gridlines, labels, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790598738-m5VRIT.jpg)

- **A.** At \(200\text{ K}\), the reaction is under thermodynamic control because the lower activation energy of transition state \(\text{TS}_1\) allows the system to establish equilibrium rapidly.
- **B.** At \(200\text{ K}\), the reaction is under kinetic control because the lower activation energy allows \(\text{X(g)}\) to form faster, whereas at \(500\text{ K}\), reversibility enables the more thermodynamically stable product \(\text{Y(g)}\) to predominate.
- **C.** At \(500\text{ K}\), the reaction is under kinetic control because the higher temperature provides sufficient energy for \(\text{Y(g)}\) to form at a greater rate than \(\text{X(g)}\).
- **D.** At \(500\text{ K}\), the reaction is under thermodynamic control because increasing the temperature decreases the forward rate constant for the pathway producing \(\text{X(g)}\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123931/*