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title: "A student mixes \\(1.0\\text{ mol}\\) of \\(\\text{H}_2(g)\\) and \\(0.50\\text{ mol}\\) of \\(\\text{O}_2(g)\\) in a rigid, sealed \\(2.0\\text{ L}\\) container at \\(298\\text{ K}\\). The balanced chemical equation and standard Gibbs free energy change for the reaction are shown below. \\[ 2\\,\\text{H}_2(g) + \\text{O}_2(g) \\rightarrow 2\\,\\text{H}_2\\text{O}(g) \\quad \\Delta G^\\circ_{298} = -457\\text{ kJ/mol}_{rxn} \\] After several days at \\(298\\text{ K}\\), the student observes that no measurable amount of \\(\\text{H}_2\\text{O}(g)\\) has formed and the total pressure in the container remains unchanged. Which of the following best explains why no reaction is observed at this temperature?"
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url: "https://nerd-notes.com/ubq/119788/"
date_modified: "2026-08-21T08:12:21+00:00"
---

# A student mixes \(1.0\text{ mol}\) of \(\text{H}_2(g)\) and \(0.50\text{ mol}\) of \(\text{O}_2(g)\) in a rigid, sealed \(2.0\text{ L}\) container at \(298\text{ K}\). The balanced chemical equation and standard Gibbs free energy change for the reaction are shown below. \[ 2\,\text{H}_2(g) + \text{O}_2(g) \rightarrow 2\,\text{H}_2\text{O}(g) \quad \Delta G^\circ_{298} = -457\text{ kJ/mol}_{rxn} \] After several days at \(298\text{ K}\), the student observes that no measurable amount of \(\text{H}_2\text{O}(g)\) has formed and the total pressure in the container remains unchanged. Which of the following best explains why no reaction is observed at this temperature?

A student mixes \(1.0\text{ mol}\) of \(\text{H}_2(g)\) and \(0.50\text{ mol}\) of \(\text{O}_2(g)\) in a rigid, sealed \(2.0\text{ L}\) container at \(298\text{ K}\). The balanced chemical equation and standard Gibbs free energy change for the reaction are shown below. \[ 2\,\text{H}_2(g) + \text{O}_2(g) \rightarrow 2\,\text{H}_2\text{O}(g) \quad \Delta G^\circ_{298} = -457\text{ kJ/mol}_{rxn} \] After several days at \(298\text{ K}\), the student observes that no measurable amount of \(\text{H}_2\text{O}(g)\) has formed and the total pressure in the container remains unchanged. Which of the following best explains why no reaction is observed at this temperature?

- **A.** The reaction is thermodynamically unfavorable at \(298\text{ K}\) because the decrease in the number of moles of gas results in \(\Delta S^\circ < 0\).
- **B.** The reaction is thermodynamically unfavorable at \(298\text{ K}\) because the strong covalent bonds in \(\text{H}_2\) and \(\text{O}_2\) make \(\Delta G^\circ\) positive at room temperature.
- **C.** The reaction is under kinetic control at \(298\text{ K}\) because the activation energy is high, so very few collisions have sufficient energy to react.
- **D.** The reaction is under kinetic control at \(298\text{ K}\) because the equilibrium constant \(K\) is much less than \(1\), preventing product formation.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119788/*