The heat of combustion of carbon to $C{O}_2$ is -393.5  kJ/mol. The heat released upon formation of 35.2 g of $C{O}_2$ from carbon and oxygen gas is

Given,

${\mathrm{C}}_{\left(\mathrm{s}\right)}+{\mathrm{O}}_{2( \mathrm{g})}⟶{\mathrm{CO}}_{2( \mathrm{g})},\Delta H=-393.5 \mathrm{kJ}/\mathrm{mol}$

Amount of heat released on formation of $44 {\mathrm{gCO}}_2=393.5 \mathrm{kJ}$

$\therefore \text{ Amount of heat released on formation of }35.2 {\mathrm{gCO}}_2$

$=-\frac{393.5}{44}\times 35.2$

$=-314.8\approx -315 \mathrm{kJ}$