$C + \frac{1}{2} O_2 \to CO; \Delta H = -42 \ kJ$
$CO + \frac{1}{2} O_2 \to CO_2; \Delta H = -24 \ kJ$
The heat of formation of $CO_2$ is ..... $kJ$.

Find the standard enthalpy of formation of $SO_{3(g)}$ from the following reactions:
$S_{8(s)} + 8O_{2(g)} \to 8SO_{2(g)}$; $\Delta H_1 = -2775 \ kJ/mol$
$2SO_{2(g)} + O_{2(g)} \to 2SO_{3(g)}$; $\Delta H_2 = -198 \ kJ/mol$

When $50 \ cm^3$ of a strong acid is added to $50 \ cm^3$ of an alkali,the temperature rises by $5 \ ^oC$. If $250 \ cm^3$ of each liquid are mixed,the temperature rise would be $... \ ^oC$.

Calculate the enthalpy change of the reaction for $H_2(g) + Cl_2(g) \rightarrow 2HCl(g)$, given the bond energies (in $\text{kJ mol}^{-1}$): $H-H = 436$, $Cl-Cl = 242$, $H-Cl = 431$.

Which of the following statements is correct for the enthalpy of combustion?

What is the quantity of heat evolved when $6 \ g$ of carbon combines with sulphur to form $CS_2$ according to the reaction $C + 2S \rightarrow CS_2 \quad \Delta H = 92 \ kJ \ mol^{-1}$ (in $kJ$)?