to calculate ΔH of reaction, let's use the following formula
ΔH of reaction= [ΔH of products] - [ΔH of reactants]
note: keep in mind that you have to multiply each value by its coefficient.
ΔH of reaction= [ ΔH CO2 + ΔH H2O + ΔH Na2CO3] - [ΔH NaHCO3]
ΔH of reaction = [ -393.5 + -241.8 + -1130.9] - [ 2 x -947.7]
ΔH of reaction= 129.2 kJ
since ΔH is positive, the reaction is endothermic
