For an endothermic reaction, where `Delta H` represents the enthalpy of reaction in `kJ mol^(-1)`, the minimum value for the energy of activation will be

Options

A. Less the zero
B. equal to `Delta H`
C. less than `Delta H`
D. more than `Delta H`

Answer

To find the minimum value for the energy of activation (Ea) for an endothermic reaction, we can follow these steps:

### Step 1: Understand the nature of endothermic reactions
In an endothermic reaction, the enthalpy change (ΔH) is positive. This means that the energy of the products is higher than that of the reactants.

### Step 2: Visualize the energy profile
Draw an energy versus reaction coordinate diagram. In this diagram:
- The reactants are at a lower energy level.
- The products are at a higher energy level.
- The difference in energy between the reactants and products is ΔH.

### Step 3: Identify activation energy
In the energy profile:
- The activation energy (Ea) for the forward reaction is the energy required to reach the transition state from the reactants.
- The activation energy for the backward reaction is the energy required to reach the transition state from the products.

### Step 4: Relate ΔH and activation energies
The relationship between the activation energies and ΔH can be expressed as:
\[ \Delta H = E_a (\text{forward}) - E_a (\text{backward}) \]
This means that the activation energy for the forward reaction is greater than ΔH because the reactants need to overcome the energy barrier to reach the products.

### Step 5: Conclude the minimum value of activation energy
Since the activation energy for the forward reaction must be greater than the enthalpy change (ΔH) for an endothermic reaction, we can conclude:
\[ E_a (\text{forward}) > \Delta H \]
Thus, the minimum value for the energy of activation will be greater than ΔH.

### Final Answer
The minimum value for the energy of activation (Ea) for an endothermic reaction is greater than ΔH.

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