Enthalpy of combustion of ${\mathrm{C}}_6{{\mathrm{H}}_6}_{ \left(\mathrm{l}\right)}$at $298 \mathrm{K}$ to yield ${\mathrm{CO}}_{2 \left(\mathrm{g}\right)}$ and ${\mathrm{H}}_2{\mathrm{O}}_{ \left(\mathrm{l}\right)}$is $∆\mathrm{H} = –781.1 \mathrm{kcal}.$ Calculate $∆\mathrm{U}.$    

 

Which among the following thermochemical equations represent the formation of sodium chloride?

Enthalpy of formation of two compounds $\mathrm{x}$ and $\mathrm{y}$ are $\text{-84 kJ and -156 kJ}$, respectively. Which of the following statements is CORRECT?    

Heat of formation of water is $-272 \mathrm{kJ}$. How much water can be decomposed by $750 \mathrm{kJ}$ of heat?

${\mathrm{H}}_{\mathrm{2}}+{\mathrm{Cl}}_{\mathrm{2}}\mathrm{ }\stackrel{}{\to }2\mathrm{HCl}; ∆\mathrm{H} = -184 \mathrm{kJ}/\mathrm{mole}$

Then, what is the amount of energy absorbed when $0.365 \mathrm{kg}$ of $\mathrm{HCl}$ is formed?