Calculate the heat of a reaction
in order to calculate the heat of reaction, you need the bond energies (which are measured in $\mathrm{kJ/mol}$ and usually provided in the question or in an appendix in the back of the chemistry book). The heat of reaction is equal to the energy of bonds broken minus the energy of the bonds created. It would be equal:

$[4*(\ce{S-O} $ bond energy$) ~+ ~1*(\ce{O=O} $ bond energy$)] - [6*(\ce{S-O} $ bond energy$)]$.

This will give a negative answer if the reaction is exothermic and vice versa. Since it is measured in $\mathrm{kJ/mol}$, multiply by moles to get the total energy released.