- Dynamic equilibrium occurs when the forward and reverse reaction rates are equal.
- Macroscopic properties like concentration remain constant because the net change is zero.
- The forward and reverse reactions do not stop, but their net effect is constant.
- The correct statement is: \(\boxed{\text{The concentrations of the products and reactants do not change.}}\)
Explanation
- Analyzing Dynamic Equilibrium
The chemical reaction provided is \(2 \text{N}_2\text{O}_5(g) \rightleftharpoons 4 \text{NO}_2(g) + \text{O}_2(g)\), and the system is at dynamic equilibrium at a constant temperature of \(500 \text{ K}\). Dynamic equilibrium occurs in reversible reactions when the rate of the forward reaction equals the rate of the reverse reaction. In this state, there is no net change in the concentrations of the reactants and products, even though both the forward and reverse processes continue to occur at the same rate.
- Evaluating the Statements
Now, we evaluate the given statements:
- "The concentrations of the products and reactants do not change.": This is true. At equilibrium, the system's composition remains constant over time.
- "The forward reaction stops at \(500 \text{ K}\).": This is false. Reactions at equilibrium do not stop; they continue at the microscopic level.
- "The forward and reverse reactions no longer occur.": This is false. Both processes continue to take place at equal rates.
- "The rates of the forward and reverse reactions are unequal.": This is false. The defining characteristic of dynamic equilibrium is that the rates are equal.
- Conclusion
Based on the principles of chemical equilibrium, the only statement that correctly describes the state of the system is the first one. Therefore, at dynamic equilibrium, the macroscopic concentrations of all substances involved remain constant over time.
Examples
Imagine a busy bridge with cars driving in both directions. At 'equilibrium', the number of cars entering the bridge from one side equals the number of cars exiting that side, meaning the total number of cars on the bridge remains constant. Similarly, in a chemical reaction at dynamic equilibrium, the forward and reverse rates are equal, ensuring the concentrations of reactants and products stay the same despite the continuous microscopic activity.