The values of heat of formation of ${\mathrm{SO}}_{2 }\mathrm{and} {\mathrm{SO}}_3$ are $-398.2\mathrm{kJ}\text{ and }-198.2\mathrm{kJ}\text{. }$The heat of reaction of the following reaction will be ${\mathrm{SO}}_2+\frac{1}{2}{\mathrm{O}}_2\to {\mathrm{SO}}_3$