Energy Calculations ( The return of the MOLE(>o<))

ΔH is the energy change that takes place in an reaction and is expressed in kJ/mole. It can be on both sides of a chemical equation. If it's on the left hand side (LHS) of the equation which is terminologically called reactants, it's a endothermic reaction that loses energy. If it's on the right hand side (RHS), the reaction, it's called exothermic.

Now, in order to do a energy calculation, one just need to use the ΔH/the coefficients of the balanced equations to find out how much energy released/absorbed from the substances.

EX. C3H8 + 5O2 -----> 3CO2 + 4H2O + 1050kJ
       so,   __-1050kJ___          or          __-1050kJ__  = __-210kJ__
              1 mol of C3H8                         5 mols of O2      1 mol of O2

NOTE: ΔH (energy change) differentiates base on what chemical reaction one is preceeding.

Examples of more advance energy calculations: