- Dynamic equilibrium means the forward and reverse reactions occur at equal rates.
- Constant concentrations are maintained because the rates are equal.
- Calcium carbonate is formed by the forward reaction, and calcium oxide is formed by the reverse reaction.
- Therefore, the rates of formation of these substances must be equal at equilibrium.
- The correct statement is: \(\boxed{\text{Calcium carbonate and calcium oxide are formed at the same rate.}}\)
Explanation
- Understanding Dynamic Equilibrium
In a reversible chemical reaction at dynamic equilibrium, such as \(CaO(s) + CO_2(g) \rightleftharpoons CaCO_3(s)\), both the forward and reverse reactions are occurring simultaneously. The term "dynamic" implies that the reactions have not ceased; instead, they continue at equal rates. Consequently, the net concentrations of all reactants and products remain constant over time.
- Evaluating the Options
Let's analyze the given options based on the principles of equilibrium:
- The concentration of calcium carbonate is increasing: This is incorrect because at dynamic equilibrium, the concentrations of all reactants and products remain constant.
- The reaction has run out of carbon dioxide or calcium oxide: This is incorrect because equilibrium implies that both reactants and products are present in the system simultaneously.
- The forward and reverse reactions have stopped: This is incorrect because dynamic equilibrium is characterized by the continuous occurrence of both forward and reverse reactions, not their cessation.
- Calcium carbonate and calcium oxide are formed at the same rate: In the forward reaction, \(CaCO_3\) is formed. In the reverse reaction, \(CaO\) is formed. Since the rate of the forward reaction equals the rate of the reverse reaction at equilibrium, the rate at which \(CaCO_3\) is produced is equal to the rate at which \(CaO\) is produced. This statement is correct.
- Final Conclusion
Based on the analysis, the statement that must be true at dynamic equilibrium is that calcium carbonate and calcium oxide are formed at the same rate. This is a direct consequence of the definition of dynamic equilibrium, where the rate of the forward reaction equals the rate of the reverse reaction. The correct choice is the second option.
Examples
Dynamic equilibrium is essential in industrial processes like the Haber-Bosch process for ammonia production. Engineers must manage temperature and pressure to ensure the rate of ammonia production remains optimal without the reaction stopping. Similarly, understanding the equilibrium of calcium carbonate is vital in geological processes, such as the formation of stalactites and stalagmites in caves, where limestone dissolves and precipitates based on environmental conditions.