I have a sheet on Hess's Law where Enthalpy change is sometimes given as kJ and other times kJ/mol.
Why? What's the difference?

The latter is given as "The heat of vaporisation of water is 44kJ/mol. Calculate the heat of reaction [gaseous ethanol]... "
Why is it kJ/mol and should the heat of reaction be given as kJ or kJ/mol?

Enthalpy is measured in kJ/mole. The heat of reaction may also be expressed in kJ/mole, but if you know how many moles of material are involved you can calculate the total heat released (or absorbed) by a reaction in kJ. Converesely, in a lab experiment you might measure the heat produced in kJ, and the calculate the enthalpy of the materials in terms of kJ/mole.