Here's how to calculate the enthalpy change (ΔH) in kJ/mol:

1. Calculate the energy per mole:

* Divide the total energy used by the number of moles:

12 J / 3 moles = 4 J/mol

2. Convert Joules to Kilojoules:

* There are 1000 Joules in 1 Kilojoule:

4 J/mol * (1 kJ / 1000 J) = 0.004 kJ/mol

Therefore, the enthalpy change (ΔH) is 0.004 kJ/mol.