Which of these is a characteristic of the state of equilibrium?

Options

A. Temperature is constant
B. `"Rate"_(f)="Rate"_(b)`
C. Conc. of reactants & products are constant
D. All of these

Answer

To determine the characteristic of the state of equilibrium, let's analyze the options provided:

1. **Understanding Equilibrium**:
- In a chemical reaction, equilibrium is the state where the rates of the forward and reverse reactions are equal. This means that the concentration of reactants and products remains constant over time.

2. **Analyzing the Options**:
- **Option A: Temperature is constant**:
- In a state of equilibrium, the temperature does not change. This is true.
- **Option B: Rate of forward reaction equals rate of backward reaction**:
- This is a defining characteristic of equilibrium. At equilibrium, the rate at which reactants are converted to products is equal to the rate at which products are converted back to reactants. This is also true.
- **Option C: Concentration of reactants and products are constant**:
- At equilibrium, the concentrations of both reactants and products remain constant, although they are not necessarily equal. This is also true.
- **Option D: All of these**:
- Since options A, B, and C are all correct, option D, which states "all of these," is also correct.

3. **Conclusion**:
- The correct answer is **D: All of these**. All the statements about the characteristics of the state of equilibrium are true.

### Step-by-Step Solution:
1. Identify the characteristics of equilibrium.
2. Analyze each option provided:
- Check if temperature remains constant.
- Verify if the rate of forward reaction equals the rate of backward reaction.
- Confirm if the concentration of reactants and products remains constant.
3. Conclude that since all individual statements are true, the answer is option D: All of these.