Consider the reaction:

[tex]2 \text{SO}_2(g) + \text{O}_2(g) \longleftrightarrow 2 \text{SO}_3(g)[/tex]

When does the given chemical system reach dynamic equilibrium?

A. When the forward and reverse reactions stop.
B. When the rate of the forward reaction is higher than the rate of the reverse reaction.
C. When the concentration of the reactants is higher than the concentration of the products.
D. When the rates of the forward and reverse reactions are equal.



Answer :

The chemical system reaches dynamic equilibrium when the rates of the forward and reverse reactions are equal. Here’s a step-by-step explanation:

1. Understanding Dynamic Equilibrium:
- In a chemical reaction, dynamic equilibrium is the state where the rate of the forward reaction equals the rate of the reverse reaction.
- At dynamic equilibrium, the concentrations of the reactants and products remain constant over time, although both reactions continue to occur.

2. Examining Alternatives:
- When the forward and reverse reactions stop: This does not describe dynamic equilibrium. Even at equilibrium, both reactions continue to occur, but their rates are equal.
- When the rate of the forward reaction is higher than the rate of the reverse reaction: This would result in a net conversion of reactants to products, indicating the system is not at equilibrium.
- When the concentration of the reactants is higher than the concentration of the products: Concentration alone does not define dynamic equilibrium. The system could have higher concentrations of reactants or products, but what matters is the rate of the reactions.

3. Correct Answer:
- When the rates of the forward and reverse reactions are equal: This correctly describes the condition for dynamic equilibrium. No net change in the concentration of reactants and products occurs because the two reaction rates balance each other.

Therefore, the chemical system reaches dynamic equilibrium when the rates of the forward and reverse reactions are equal.