The balanced reaction for the decomposition of baking soda is
2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
We can find the heat of reaction by using the Hess' Law. This is done by using this formula:
∑(Hf,products) -∑(Hf,reactants) = Heat of reaction
where Hf is the heat of formation. According to literature, these are the heats of formation for each of the compounds in the reaction:
NaHCO3: -947.68 kJ/mol
Na2CO3: -1130.94 kJ/mol
CO2: -393.51 kJ/mol
H2O: -241.8 kJ/mol
Applying Hess' Law:
[1(-1130.94) + 1(-241.82)] + 1(-393.51)] - [2(-947.68)] = 129.09 kJ
Thus, the heat of reaction is 129.09 kJ/mol NaHCO3. Since there is 1.96 mol of NaHCO3, the total heat of reaction is 253.02 kJ.
