To determine when the chemical system reaches dynamic equilibrium for the reaction
[tex]\[ 2 \text{SO}_2(g) + \text{O}_2(g) \longleftrightarrow 2 \text{SO}_3(g) \][/tex]
we need to understand the concept of dynamic equilibrium in the context of chemical reactions. Let's go through the concepts step by step:
### Dynamic Equilibrium in Chemical Reactions
1. Definition of Dynamic Equilibrium:
- Dynamic equilibrium occurs in a closed system when the rate of the forward reaction equals the rate of the reverse reaction.
- At dynamic equilibrium, there is no overall change in the concentrations of reactants and products, though both reactions continue to occur.
2. Characteristics of Dynamic Equilibrium:
- The system is closed, meaning no substances are added or removed from the system.
- The rates of the forward and reverse reactions are exactly balanced.
- The concentrations of reactants and products remain constant over time, though not necessarily equal.
- Dynamic equilibrium is different from a static equilibrium because reactions continue to proceed in both directions.
### Applying This Concept to the Given Reaction
Given the reaction:
[tex]\[ 2 \text{SO}_2(g) + \text{O}_2(g) \longleftrightarrow 2 \text{SO}_3(g) \][/tex]
To determine when this reaction reaches dynamic equilibrium, let's explore the given options:
- When the forward and reverse reactions stop:
- This is incorrect because at equilibrium, reactions continue in both directions.
- When the rate of the forward reaction is higher than the rate of the reverse reaction:
- This is incorrect because dynamic equilibrium occurs when the forward and reverse reaction rates are equal.
- When the concentration of the reactants is higher than the concentration of the products:
- This is not necessarily a criterion for dynamic equilibrium. The concentrations of reactants and products can vary at equilibrium.
- When the rates of the forward and reverse reactions are equal:
- This is correct. Dynamic equilibrium is achieved when the rate of the forward reaction is equal to the rate of the reverse reaction.
### Conclusion
The chemical system reaches dynamic equilibrium when the rates of the forward and reverse reactions are equal. This means the correct answer is:
- When the rates of the forward and reverse reactions are equal
