The heat of combustion of acetaldehyde to carbon dioxide and water is $-1172 \ kJ \ mol^{-1}$. Calculate the amount of heat liberated when $66 \ g$ of acetaldehyde is completely oxidised. (Atomic mass: $C=12, H=1, O=16$) (in $kJ$)

Calculate the heat of reaction for the process: $NH_3(g) + HCl(g) \rightarrow NH_4Cl(s)$ given the following data:
$(i)$ $NH_3(g) + aq \rightarrow NH_3(aq)$,$\Delta H = -8.4 \, Kcal$
$(ii)$ $HCl(g) + aq \rightarrow HCl(aq)$,$\Delta H = -17.3 \, Kcal$
$(iii)$ $NH_3(aq) + HCl(aq) \rightarrow NH_4Cl(aq)$,$\Delta H = -12.5 \, Kcal$
$(iv)$ $NH_4Cl(s) + aq \rightarrow NH_4Cl(aq)$,$\Delta H = +3.9 \, Kcal$ (in $, Kcal$)

If the combustion of $1 \ g$ of graphite produces $20.7 \ kJ$ of heat,what will be the molar enthalpy change? Give the significance of the sign also.

Carbon and carbon monoxide burn in oxygen to form carbon dioxide according to the following reactions:
$C(s) + O_2(g) \to CO_2(g)$; $\Delta H = -394 \ kJ \ mol^{-1}$
$2CO(g) + O_2(g) \to 2CO_2(g)$; $\Delta H = -569 \ kJ \ mol^{-1}$
The heat of formation of $1 \ mol$ of carbon monoxide is thus ..... $kJ \ mol^{-1}$.

Given
$N_{2(g)} + 3H_{2(g)} \longrightarrow 2NH_{3(g)} \quad \Delta_{r}H^{\theta} = -92.4 \, kJ \, mol^{-1}$
What is the standard enthalpy of formation of $NH_{3}$ gas?

Which of the following statements is correct about the heat of combustion?