Question

The decomposition of dinitrogen pentaoxide has and activation energy of 102 kj/mol and delta H degree rsn = + 55 kj/mol. What is the activation energy for the reverse reaction?

a. 27 kj/mol
b. 47 kj/mol
c. 55 kj/mol
d. 102 kj/mol
e. more information is needed, since this is a Hess's law calculation

Answer 1

To calculate the activation energy for the reverse reaction of the decomposition of dinitrogen pentoxide, you simply add the forward reaction's activation energy (102 kJ/mol) and the reaction's enthalpy change (+55 kJ/mol), giving us 157 kJ/mol.

Step-by-step explanation:

The activation energy (Ea) for a reaction and the enthalpy change (ΔH) of that reaction are related to the activation energy for the reverse reaction. The activation energy for the reverse reaction can be calculated using the equation Ea(reverse) = Ea(forward) + ΔH. Given that the activation energy for the decomposition of dinitrogen pentoxide is 102 kJ/mol and the enthalpy change is +55 kJ/mol, we can calculate the activation energy for the reverse reaction.

Ea(reverse) = Ea(forward) + ΔH = 102 kJ/mol + 55 kJ/mol = 157 kJ/mol.

The correct answer is option e, 'more information is needed, since this is a Hess's law calculation'. This is because the calculation for the activation energy for the reverse reaction does not rely on Hess's Law, which is used for calculating enthalpy changes of reactions, not activation energies.