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title: "A student investigates four different reversible gas-phase reactions at \\(500\\text{ K}\\). Each reaction is allowed to reach chemical equilibrium in a separate rigid container. The balanced chemical equations and the measured equilibrium partial pressures of all species are shown in the table below.  | System | Balanced equation | Equilibrium partial pressures (\\(\\text{atm}\\)) | | :— | :— | :— | | 1 | \\(2\\,\\text{NO}_2(g) \\rightleftharpoons \\text{N}_2\\text{O}_4(g)\\) | \\(P_{\\text{NO}_2} = 2.0\\), \\(P_{\\text{N}_2\\text{O}_4} = 0.40\\) | | 2 | \\(\\text{CO}(g) + \\text{Cl}_2(g) \\rightleftharpoons \\text{COCl}_2(g)\\) | \\(P_{\\text{CO}} = 0.10\\), \\(P_{\\text{Cl}_2} = 0.10\\), \\(P_{\\text{COCl}_2} = 4.0\\) | | 3 | \\(2\\,\\text{NOCl}(g) \\rightleftharpoons 2\\,\\text{NO}(g) + \\text{Cl}_2(g)\\) | \\(P_{\\text{NOCl}} = 1.0\\), \\(P_{\\text{NO}} = 0.20\\), \\(P_{\\text{Cl}_2} = 0.10\\) | | 4 | \\(\\text{PCl}_5(g) \\rightleftharpoons \\text{PCl}_3(g) + \\text{Cl}_2(g)\\) | \\(P_{\\text{PCl}_5} = 2.0\\), \\(P_{\\text{PCl}_3} = 0.50\\), \\(P_{\\text{Cl}_2} = 0.50\\) |  Based on the data in the table, which system is product-favored at \\(500\\text{ K}\\), and why?"
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url: "https://nerd-notes.com/ubq/120306/"
date_modified: "2026-08-23T04:04:28+00:00"
---

# A student investigates four different reversible gas-phase reactions at \(500\text{ K}\). Each reaction is allowed to reach chemical equilibrium in a separate rigid container. The balanced chemical equations and the measured equilibrium partial pressures of all species are shown in the table below.

| System | Balanced equation | Equilibrium partial pressures (\(\text{atm}\)) |
| :— | :— | :— |
| 1 | \(2\,\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\) | \(P_{\text{NO}_2} = 2.0\), \(P_{\text{N}_2\text{O}_4} = 0.40\) |
| 2 | \(\text{CO}(g) + \text{Cl}_2(g) \rightleftharpoons \text{COCl}_2(g)\) | \(P_{\text{CO}} = 0.10\), \(P_{\text{Cl}_2} = 0.10\), \(P_{\text{COCl}_2} = 4.0\) |
| 3 | \(2\,\text{NOCl}(g) \rightleftharpoons 2\,\text{NO}(g) + \text{Cl}_2(g)\) | \(P_{\text{NOCl}} = 1.0\), \(P_{\text{NO}} = 0.20\), \(P_{\text{Cl}_2} = 0.10\) |
| 4 | \(\text{PCl}_5(g) \rightleftharpoons \text{PCl}_3(g) + \text{Cl}_2(g)\) | \(P_{\text{PCl}_5} = 2.0\), \(P_{\text{PCl}_3} = 0.50\), \(P_{\text{Cl}_2} = 0.50\) |

Based on the data in the table, which system is product-favored at \(500\text{ K}\), and why?

A student investigates four different reversible gas-phase reactions at \(500\text{ K}\). Each reaction is allowed to reach chemical equilibrium in a separate rigid container. The balanced chemical equations and the measured equilibrium partial pressures of all species are shown in the table below.

| System | Balanced equation | Equilibrium partial pressures (\(\text{atm}\)) |
| :--- | :--- | :--- |
| 1 | \(2\,\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)\) | \(P_{\text{NO}_2} = 2.0\), \(P_{\text{N}_2\text{O}_4} = 0.40\) |
| 2 | \(\text{CO}(g) + \text{Cl}_2(g) \rightleftharpoons \text{COCl}_2(g)\) | \(P_{\text{CO}} = 0.10\), \(P_{\text{Cl}_2} = 0.10\), \(P_{\text{COCl}_2} = 4.0\) |
| 3 | \(2\,\text{NOCl}(g) \rightleftharpoons 2\,\text{NO}(g) + \text{Cl}_2(g)\) | \(P_{\text{NOCl}} = 1.0\), \(P_{\text{NO}} = 0.20\), \(P_{\text{Cl}_2} = 0.10\) |
| 4 | \(\text{PCl}_5(g) \rightleftharpoons \text{PCl}_3(g) + \text{Cl}_2(g)\) | \(P_{\text{PCl}_5} = 2.0\), \(P_{\text{PCl}_3} = 0.50\), \(P_{\text{Cl}_2} = 0.50\) |

Based on the data in the table, which system is product-favored at \(500\text{ K}\), and why?

- **A.** System 1, because \(K_p = 10\), and a value of \(K_p > 1\) indicates that products predominate at equilibrium.
- **B.** System 2, because \(K_p = 400\), and a value of \(K_p > 1\) indicates that products predominate at equilibrium.
- **C.** System 3, because \(K_p = 50\), and a value of \(K_p > 1\) indicates that products predominate at equilibrium.
- **D.** System 4, because \(K_p = 0.125\), and a value of \(K_p > 0\) indicates that products predominate at equilibrium.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120306/*