Assertion: The enthalpy of both graphite and diamond is taken to be zero, being elementary substances.

Reason: The enthalpy of formation of an elementary substance in any state is taken as zero.

If at $298 \mathrm{K}$, the bond energies of $\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, \mathrm{C}=\mathrm{C}$ and $\mathrm{H}-\mathrm{H}$ bonds are, respectively $414, 347, 615$ and $435 \mathrm{kJ} {\mathrm{mol}}^{-1}$, the value of enthalpy change for the reaction.

Assertion: A reaction spontaneous if ${\mathrm{E}}_{\mathrm{cell}}=+\mathrm{Ve}$.

Reason: For ${\mathrm{E}}_{\mathrm{cell}}=+\mathrm{ve},\mathrm{\Delta G}$ is always $-\mathrm{ve}$.

From the given reactions
$\mathrm{S} \left(\mathrm{s}\right)+\frac{{\displaystyle 3}}{{\displaystyle 2}}{\mathrm{O}}_2 \left(\mathrm{g}\right)⟶{\mathrm{SO}}_3 \left(\mathrm{g}\right)+2\mathrm{x} \mathrm{kcal}$

and ${\mathrm{SO}}_2 \left(\mathrm{g}\right)+\frac{{\displaystyle 1}}{{\displaystyle 2}}{\mathrm{O}}_2 \left(\mathrm{g}\right)⟶{\mathrm{SO}}_3 \left(\mathrm{g}\right)+\mathrm{y} \mathrm{kcal}$

the heat of formation of ${\mathrm{SO}}_2$ is: