Calculate $\Delta_r H$ $(kJ \ mol^{-1})$ of the following reaction:
$C_2H_5OH_{(l)} + \frac{7}{2}O_{2(g)} \rightarrow 2CO_{2(g)} + 3H_2O_{(l)}$

Molecule	$\Delta_f H^0 (kJ \ mol^{-1})$
$C_2H_5OH_{(l)}$	$-280$
$CO_{2(g)}$	$-400$
$H_2O_{(l)}$	$-290$

Average $C-H$ bond energy is $416 \ kJ \ mol^{-1}$. Which of the following is correct?

What will be the heat of formation of methane,if the heat of combustion of carbon is $-x \ kJ$,heat of formation of water is $-y \ kJ$ and heat of combustion of methane is $z \ kJ$?

What is enthalpy of reaction?

The bond energies of $H-H$ and $Cl-Cl$ are $430 \, kJ \, mol^{-1}$ and $240 \, kJ \, mol^{-1}$ respectively. If the value of ${\Delta _f}H$ for $HCl$ is $-90 \, kJ \, mol^{-1}$,then the $H-Cl$ bond energy is ..... $kJ \, mol^{-1}$.

Given the following thermochemical equations:
$1) \ C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)}, \Delta H = -787 \ kJ$
$2) \ H_{2(g)} + \frac{1}{2} O_{2(g)} \rightarrow H_2O_{(l)}, \Delta H = -286 \ kJ$
$3) \ C_2H_{2(g)} + \frac{5}{2} O_{2(g)} \rightarrow 2CO_{2(g)} + H_2O_{(l)}, \Delta H = -1310 \ kJ$
Calculate the enthalpy of formation of acetylene $(C_2H_{2(g)})$ in $kJ \ mol^{-1}$.