The calculation of Enthalpy is possibly done in a very simple way, and it is because it makes it possible to find the right answer.
However, the first thing you need is data that looks like this:
Click on an empty cell (1), and type in the formula =(C4*B4) + B5*(C5+C6*B6) (2), and press enter.
Enthalpy change has been caclulated.