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title: "A sample of pure solid calcium carbonate, \\(\\text{CaCO}_3(s)\\), is placed in an evacuated, rigid container and heated to \\(1000\\text{ K}\\), where it undergoes thermal decomposition according to the following reversible process:  \\[\\text{CaCO}_3(s) \\rightleftharpoons \\text{CaO}(s) + \\text{CO}_2(g)\\]  At this temperature, the equilibrium constant is \\(K_p = 0.050\\). Additional \\(\\text{CO}_2(g)\\) is added to the container such that the instantaneous partial pressure of carbon dioxide is \\(P_{\\text{CO}_2} = 0.20\\text{ atm}\\) in the presence of both solids. Which of the following gives the correct expression for the reaction quotient, \\(Q_p\\), and correctly predicts the direction of the net process required to establish equilibrium?"
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url: "https://nerd-notes.com/ubq/120273/"
date_modified: "2026-08-23T04:04:11+00:00"
---

# A sample of pure solid calcium carbonate, \(\text{CaCO}_3(s)\), is placed in an evacuated, rigid container and heated to \(1000\text{ K}\), where it undergoes thermal decomposition according to the following reversible process:

\[\text{CaCO}_3(s) \rightleftharpoons \text{CaO}(s) + \text{CO}_2(g)\]

At this temperature, the equilibrium constant is \(K_p = 0.050\). Additional \(\text{CO}_2(g)\) is added to the container such that the instantaneous partial pressure of carbon dioxide is \(P_{\text{CO}_2} = 0.20\text{ atm}\) in the presence of both solids. Which of the following gives the correct expression for the reaction quotient, \(Q_p\), and correctly predicts the direction of the net process required to establish equilibrium?

A sample of pure solid calcium carbonate, \(\text{CaCO}_3(s)\), is placed in an evacuated, rigid container and heated to \(1000\text{ K}\), where it undergoes thermal decomposition according to the following reversible process:

\[\text{CaCO}_3(s) \rightleftharpoons \text{CaO}(s) + \text{CO}_2(g)\]

At this temperature, the equilibrium constant is \(K_p = 0.050\). Additional \(\text{CO}_2(g)\) is added to the container such that the instantaneous partial pressure of carbon dioxide is \(P_{\text{CO}_2} = 0.20\text{ atm}\) in the presence of both solids. Which of the following gives the correct expression for the reaction quotient, \(Q_p\), and correctly predicts the direction of the net process required to establish equilibrium?

- **A.** \(Q_p = P_{\text{CO}_2}\); because \(Q_p > K_p\), a net reverse reaction occurs to form more \(\text{CaCO}_3(s)\).
- **B.** \(Q_p = P_{\text{CO}_2}\); because \(Q_p > K_p\), a net forward reaction occurs to produce more \(\text{CaO}(s)\).
- **C.** \(Q_p = \dfrac{P_{\text{CO}_2}\,[\text{CaO}]}{[\text{CaCO}_3]}\); because \(Q_p > K_p\), a net reverse reaction occurs to form more \(\text{CaCO}_3(s)\).
- **D.** \(Q_p = \dfrac{1}{P_{\text{CO}_2}}\); because \(Q_p < K_p\), a net forward reaction occurs to produce more \(\text{CO}_2(g)\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120273/*