In a chemical reaction, equilibrium is said to have been established when the

Options

A. opposing reacation ceases
B. concentrations of reactants and product are equal
C. velocity of opposing reaction is the same as that of forward reaction
D. reaction ceases to generate heat

Answer

To determine when a chemical reaction reaches equilibrium, we need to analyze the options provided in the question.

### Step-by-Step Solution:

1. **Understanding Equilibrium**:
- Equilibrium in a chemical reaction occurs when the rates of the forward and reverse reactions are equal. This means that the rate at which reactants are converted into products is the same as the rate at which products are converted back into reactants.

2. **Evaluating the Options**:
- **Option A**: "Opposing reaction ceases."
- This is incorrect because at equilibrium, both the forward and reverse reactions continue to occur, but at equal rates. Therefore, the opposing reaction does not stop.

- **Option B**: "Concentration of the reactants and products are equal."
- This is also incorrect. At equilibrium, the concentrations of reactants and products do not have to be equal; they just need to be constant over time.

- **Option C**: "Velocity of the opposing reaction is same as that of the forward reaction."
- This is correct. At equilibrium, the rate (or velocity) of the forward reaction is equal to the rate of the reverse reaction.

- **Option D**: "Reaction ceases to generate heat."
- This option is incorrect as well. The generation of heat is not a criterion for establishing equilibrium and does not stop at equilibrium.

3. **Conclusion**:
- The correct answer is **Option C**: "Velocity of the opposing reaction is same as that of the forward reaction."