Question

For the reaction A2 + B2 → 2AB, where Ea(fwd) = 188 kJ/mol and Ea(rev) = 65 kJ/mol, assuming the reaction occurs in one step, calculate ΔH°rxn?

Answer 1

The standard enthalpy change (ΔH°_rxn) for the reaction A2 + B2 → 2AB is calculated by subtracting the activation energy for the reverse reaction (65 kJ/mol) from the activation energy for the forward reaction (188 kJ/mol), which results in a ΔH°_rxn of 123 kJ/mol.

Step-by-step explanation:

To calculate the standard enthalpy change (ΔH°_rxn) for the reaction A2 + B2 → 2AB, given that the activation energy for the forward reaction (Ea(fwd)) is 188 kJ/mol and the activation energy for the reverse reaction (Ea(rev)) is 65 kJ/mol, we can use the relationship between activation energies and the enthalpy change of the reaction.

This relationship is based on the fact that the activation energy for the forward reaction is equal to the sum of the enthalpy change of the reaction plus the activation energy for the reverse reaction (ΔH°_rxn + Ea(rev) = Ea(fwd)).

Using this relationship, we can solve for ΔH°_rxn:

• ΔH°_rxn = Ea(fwd) - Ea(rev)
• ΔH°_rxn = 188 kJ/mol - 65 kJ/mol
• ΔH°_rxn = 123 kJ/mol

Therefore, the standard enthalpy change for the reaction is 123 kJ/mol.