Given that:
$2C_{(s)} + 2O_{2(g)} \to 2CO_{2(g)}$; $\Delta H = -787 \ kJ$
$H_{2(g)} + \frac{1}{2} O_{2(g)} \to H_2O_{(l)}$; $\Delta H = -286 \ kJ$
$C_2H_{2(g)} + \frac{5}{2} O_{2(g)} \to 2CO_{2(g)} + H_2O_{(l)}$; $\Delta H = -1301 \ kJ$
Calculate the heat of formation of acetylene $(C_2H_{2(g)})$ in $kJ$.

Given two processes:
$\frac{1}{2} P_{4(s)} + 3 Cl_{2(g)} \to 2 PCl_{3(l)} \;; \Delta H = -635 \ kJ$
$PCl_{3(l)} + Cl_{2(g)} \to PCl_{5(s)} \;; \Delta H = -137 \ kJ$
The value of the heat of formation of $PCl_{5(s)}$ is ...... $kJ \ mol^{-1}$.

The bond energies of $H-H$ and $Cl-Cl$ are $430 \, kJ \, mol^{-1}$ and $242 \, kJ \, mol^{-1}$ respectively. $\Delta H_f$ for $HCl$ is $-91 \, kJ \, mol^{-1}$. The bond energy of $HCl$ will be ............. $kJ \, mol^{-1}$.

From the following bond energies:

$H-H$ bond energy	$431.37 \text{ kJ mol}^{-1}$
$C=C$ bond energy	$606.10 \text{ kJ mol}^{-1}$
$C-C$ bond energy	$336.49 \text{ kJ mol}^{-1}$
$C-H$ bond energy	$410.50 \text{ kJ mol}^{-1}$

Enthalpy for the reaction $CH_2=CH_2 + H-H \to CH_3-CH_3$ will be .............. $\text{kJ mol}^{-1}$

Determine the enthalpy of formation for $H_2O_{2(l)}$,using the listed enthalpies of reaction:
$N_2H_{4(l)} + 2H_2O_{2(l)} \to N_{2(g)} + 4H_2O_{(l)}$; $\Delta_r H_1^o = -818 \ kJ/mol$
$N_2H_{4(l)} + O_{2(g)} \to N_{2(g)} + 2H_2O_{(l)}$; $\Delta_r H_2^o = -622 \ kJ/mol$
$H_{2(g)} + \frac{1}{2}O_{2(g)} \to H_2O_{(l)}$; $\Delta_r H_3^o = -285 \ kJ/mol$

The standard enthalpy of formation $(\Delta_f H^{\circ})$ of ammonia is $-46.2 \ kJ \ mol^{-1}$. What is the $\Delta_r H^{\circ}$ of the following reaction?
$N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)}$