Which of the following is definitely true, if for a reaction activation energies of forward and backward reactions are equal?

Options

A. `DeltaH = 0`
B. `DeltaG = 0`
C. There is no catalyst
D. The order is zero

Answer

To solve the question regarding the relationship between activation energies of forward and backward reactions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Activation Energy**:
- Activation energy (Ea) is the minimum energy required for a reaction to occur. For a reaction, there are two activation energies: one for the forward reaction (Ea forward) and one for the backward reaction (Ea backward).

2. **Given Condition**:
- The problem states that the activation energies of the forward and backward reactions are equal, i.e., Ea forward = Ea backward.

3. **Relating Activation Energy to Enthalpy Change**:
- The change in enthalpy (ΔH) for a reaction can be expressed in terms of the activation energies:
\[ ΔH = Ea \, (forward) - Ea \, (backward) \]
- Since we know that Ea forward = Ea backward, substituting this into the equation gives:
\[ ΔH = Ea \, (forward) - Ea \, (forward) = 0 \]
- Therefore, ΔH = 0.

4. **Conclusion**:
- Since the change in enthalpy (ΔH) is zero, this indicates that the energy of the reactants and products is the same. This typically occurs at equilibrium, where the forward and backward reactions occur at the same rate.

5. **Final Answer**:
- The statement that is definitely true given the condition of equal activation energies for the forward and backward reactions is that the change in enthalpy (ΔH) is zero.