-energy absorption and reduction may be laced in the equation
-exothermic reaction have the Right hand side energy term and is usually a negative ΔH
-endothermic reaction have the left hand side energy term and is usually a positive  ΔH
- ΔH=energy change of reaction and expressed in kJ/mol of one of the chemical
Eg. 2Ba+O2→2BaO+1115kJ
for this equation the exothermic reaction would be 557.5kJ/1mol Ba or 1115kJ/2mol O2
-ΔH value depends on which chemical is used in the equation
-molar mass is different for each chemical reaction, so is the ΔH for different chemical reaction
 2Ba+O2→2BaO+1115kJ
-1500kJ*-1molBa/1115kJ= 1.345mol Ba= 1.3mol Ba
Example 1:

Example 2: