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 $kJ$)

Heat of combustion of two isomers $x$ and $y$ are $17 \ kJ/mol$ and $12 \ kJ/mol$ respectively. From this information,it may be concluded that:

The standard enthalpies of combustion of $C_6H_{6(l)}$,$C(graphite)$ and $H_{2(g)}$ are respectively $-3270 \ kJ \ mol^{-1}$,$-394 \ kJ \ mol^{-1}$ and $-286 \ kJ \ mol^{-1}$. What is the standard enthalpy of formation of $C_6H_{6(l)}$ in $kJ \ mol^{-1}$?

For the reaction $2H_{2(g)} + O_{2(g)} \to 2H_2O_{(l)}$,the enthalpy change is $\Delta H = -571 \ kJ$. If the $H-H$ bond energy is $435 \ kJ \ mol^{-1}$ and the $O=O$ bond energy is $498 \ kJ \ mol^{-1}$,calculate the average bond energy of the $O-H$ bond in $kJ \ mol^{-1}$.

Energy required to dissociate $16 \ g$ of oxygen gas $(O_2)$ into free atoms is $x \ kJ$. The heat of atomisation of oxygen is:

$CuSO_{4(s)} + 5 H_2O_{(\ell)} \rightarrow CuSO_4 \cdot 5 H_2O_{(s)} ; \Delta H = -x \ kJ$. The value of $\Delta H$ represents: