Answer
To calculate $\Delta$$H$$^{\circ}_{rxn}$, subtract the enthalapies of formation of the reactants multiplied by the stoichiometric coefficients from the enthalpies of formation of the prodcuts multiplied by their stoichiometric coefficients.
Work Step by Step
$\Delta$$H$$^{\circ}_{rxn}$ $=$ $\Sigma n_p \Delta H^0_f$ $-$$\Sigma n_r \Delta H^0_f$
