When to use the unit kJ/mol

[Jonathan Zuo 2J]

Im having trouble determining when I can just write my answer in kJ and when I need to write it in kJ/mol. For example, if im trying to calculate the standard enthalpy of the reaction by using standard enthalpies of formation, which are given in kJ/mol, would I write my final answer, the standard enthalpy of the reaction, with the units of kJ/mol? Or is just kJ fine because the reaction given requires or releases that many kJ.

[Stevie Wisz]

Commenting on this because I had the same question!

[Chem_Mod]

Hi,

KJ/mol is used when you are describing the enthalpy of a reaction for 1 mole of a reactant/product.

Usually your final answer will be in KJ as you are calculating the enthalpy of a particular reaction for a given no. of moles.

For example - If you have nA + B --> C the enthalpy of this reaction will be in KJ and it indicates that the enthalpy is for n moles of A and not 1 mole.

Enthalpy of formation however is expressed in KJ/mole as it is defined as the enthalpy of reaction which leads to formation of 1 mole of that substance.