Enthalpy
Enthalpy is the heat content of a substance/group of substances.
Change in enthalpy
ΔH = heat absorbed per mole when the reaction occurs at a specific pressure
ΔH = enthalpy of products - enthalpy of reactants
Endothermic reactions : ΔH is positive
Exothermic reactions : ΔH is negative
Molar heat of combustion
The amount of heat released per unit mass or unit volume of a substance when the substance is completely burned
ΔH = -mcΔT
where m = mass of water heated
c = specific heat of water (4.18 x 10^3 J kg^-1 K^-1)
ΔT = change in temperature (final temp - intitial temp)
Hope this helps you