Question

The gas phase reaction:Cl(g) + HBr(g) →HCl(g) + Br(g)has an overall enthalpy change of −66 kJ. The activation energy for the reaction is 7 kJ.a) Draw the potential energy curve for the reaction and label Ea, ∆E, and the activated complex or transition state.b) Draw the potential curve for the reverse reaction. What is Ea? What is ∆E?

Answer 1

See the picture attached

Step-by-step explanation:

a) The original reaction has a negative enthalpy change, that means the reaction is exothermic, that is, the energy of the products is lower than the energy of the reactants (see picture). In the figure, ∆E is referred as energy released.

b) In the reverse reaction, the magnitude of ∆E is the same of the original reaction, but now the reaction is endothermic, so ∆E is positive, then ∆E = 66 kJ. In the figure, ∆E is referred as energy absorbed. As can be seen in the picture, the activation energy now is the addition of the magnitude of the enthalpy change and activation energy of the original reaction, that is, Ea = 7 kJ + 66 kJ = 73 kJ.

Answer 2

Step-by-step explanation:

Activation energy is defined as that energy which is required by the reactants to convert it into products.

The potential energy curve for the forward and backward reaction is drawn below.

where,

`E_R` = Energy of the reactants

`E_P` = Energy of the products

`E_a,f` = Activation energy for the forward reaction

`E_a,b` = Activation energy for the backward reaction

`\Delta H` = Amount of heat absorbed or released during the reaction

`\Delta H` for the forward reaction is -66 kJ.

Therefore, energy of the products will be lower as compared to the energy of the products for the forward reaction.

Activation energy for the backward reaction

`E_a,f + \Delta H = E_a, b`

`\Delta H` = 66 kJ

`E_a,f` = 7 kJ

`E_a,b` = 73 kJ