Which of the following is true ?

Options

A. In an endothermic equilibrium reaction, activation energy required for a forward reaction is higher than that for a backward reaction.
B. To an endothermic reaction, activation energy required to forward reaction is lower than that for a backward reaction.
C. Activation energy required for both forward and backward reactions is same in equilibrium.
D. No activation energy is required for an exothermic backward equilibrium reaction.

Answer

To determine which statement is true regarding activation energy in an endothermic equilibrium reaction, we can analyze the concepts of activation energy and the nature of endothermic reactions.

### Step-by-Step Solution:

1. **Understanding Endothermic Reactions**:
- In an endothermic reaction, the enthalpy change (ΔH) is positive, meaning that the system absorbs energy from the surroundings. This can be visualized through an energy profile diagram.

2. **Drawing the Energy Profile**:
- For an endothermic reaction, the energy of the products is higher than that of the reactants.
- Let's denote the energy of the reactants as A and the energy of the products as B. The activation energy (Ea) for the forward reaction is the energy required to convert reactants (A) into products (B).

3. **Activation Energy for Forward and Backward Reactions**:
- The activation energy for the forward reaction (Ea_forward) is the energy difference from the reactants (A) to the peak of the energy barrier.
- The activation energy for the backward reaction (Ea_backward) is the energy difference from the products (B) back to the peak of the energy barrier.

4. **Comparing Activation Energies**:
- In an endothermic reaction, since the products are at a higher energy level than the reactants, the activation energy for the forward reaction (Ea_forward) will be greater than the activation energy for the backward reaction (Ea_backward).
- Mathematically, we can express this as:
\[ Ea_{forward} > Ea_{backward} \]

5. **Evaluating the Options**:
- **Option A**: "In an endothermic equilibrium reaction, activation energy required for a forward reaction is higher than that of a backward reaction." - This statement is true based on our analysis.
- **Option B**: "To an endothermic reaction, the activation energy required to forward reaction is lower than that of backward reaction." - This statement is false.
- **Option C**: "Activation energy required for both forward and backward reaction is same in equilibrium." - This statement is false.
- **Option D**: "No activation energy is required for exothermic backward equilibrium reaction." - This statement is also false.

6. **Conclusion**:
- The correct answer is **Option A**: "In an endothermic equilibrium reaction, activation energy required for a forward reaction is higher than that of a backward reaction."