For the exothermic reaction` A + B rArr C + D.Delta(H)` is the heat of reaction and Ea is the activation energy. The activation energy for the formation of A+B will be

Options

A. `E_(a)`
B. `Delta(H)`
C. `E_(a) + Delta(H)`
D. `Delta(H) - E_(a)`

Explanation

To determine the activation energy for the formation of reactants A and B in the exothermic reaction \( A + B \rightleftharpoons C + D \), we can analyze the energy profile of the reaction.

### Step 1: Understand the Energy Profile Diagram
In an exothermic reaction, the energy of the reactants (A and B) is higher than the energy of the products (C and D). The difference in energy between the reactants and products is represented by the enthalpy change (\( \Delta H \)), which is negative for exothermic reactions.

**Hint:** Draw an energy profile diagram to visualize the energy changes during the reaction.

### Step 2: Identify Activation Energy for Forward Reaction
The activation energy (\( E_a \)) for the forward reaction (from A and B to C and D) is the energy required to reach the transition state from the reactants. This is the peak of the energy profile.

**Hint:** The activation energy for the forward reaction is the height of the energy barrier from the reactants to the transition state.

### Step 3: Determine Activation Energy for Backward Reaction
For the backward reaction (from C and D back to A and B), the activation energy is the energy required to convert the products back to the reactants. This can be calculated as the sum of the activation energy for the forward reaction and the enthalpy change (\( \Delta H \)) of the reaction.

**Hint:** The activation energy for the backward reaction can be expressed as:
\[ E_a (\text{backward}) = E_a (\text{forward}) + |\Delta H| \]

### Step 4: Write the Final Expression
Thus, the activation energy for the formation of A and B can be expressed as:
\[ E_a (\text{formation of A and B}) = E_a (\text{forward}) + |\Delta H| \]

**Hint:** Remember that \( |\Delta H| \) is the absolute value of the enthalpy change, which is positive since it represents the energy released during the exothermic reaction.

### Conclusion
The activation energy for the formation of A and B is given by the activation energy of the forward reaction plus the absolute value of the enthalpy change (\( \Delta H \)).

**Final Answer:**
\[ E_a (\text{formation of A and B}) = E_a (\text{forward}) + |\Delta H| \]