Observe the following reaction:
$2 A_{2(g)} + B_{2(g)} \xrightarrow{T(K)} 2 A_2 B_{(g)} + 600 \ kJ$
The standard enthalpy of formation $(\Delta_f H^{\circ})$ of $A_2 B_{(g)}$ is:

The combustion enthalpies of carbon,hydrogen,and methane are $-395.5 \, kJ \, mol^{-1}$,$-285.8 \, kJ \, mol^{-1}$,and $-890.4 \, kJ \, mol^{-1}$ respectively at $25 \, ^oC$. The value of standard formation enthalpy of methane at that temperature is ..... $kJ \, mol^{-1}$.

If the enthalpies of atomization of methane and ethane are respectively $320 \ cal$ and $360 \ cal$,then the bond energy of the $C-C$ bond is......$cal$.

The standard enthalpy of atomization of ethane according to the equation $C_2H_{6(g)} \rightarrow 2C_{(g)} + 6H_{(g)}$ is $622 \ kJ \ mol^{-1}$. If the standard mean $C-H$ bond dissociation enthalpy is $90 \ kJ \ mol^{-1}$,the standard mean dissociation enthalpy of the $C-C$ bond (in $kJ \ mol^{-1}$) is:

The standard enthalpy of formation of $NH_3$ is $-46.0 \, kJ/mol$. If the enthalpy of formation of $H_2$ from its atoms is $-436 \, kJ/mol$ and that of $N_2$ is $-712 \, kJ/mol$,the average bond enthalpy of $N-H$ bond in $NH_3$ is......$kJ/mol$

Consider the following cases of standard enthalpy of reaction $\Delta H_{r}^{\circ}$ in $kJ \ mol^{-1}$:
$C_{2}H_{6(g)} + \frac{7}{2} O_{2(g)} \rightarrow 2 CO_{2(g)} + 3 H_{2}O(\ell)$,$\Delta H_{1}^{\circ} = -1550$
$C(\text{graphite}) + O_{2(g)} \rightarrow CO_{2(g)}$,$\Delta H_{2}^{\circ} = -393.5$
$H_{2(g)} + \frac{1}{2} O_{2(g)} \rightarrow H_{2}O(\ell)$,$\Delta H_{3}^{\circ} = -286$
The magnitude of $\Delta H_{f, C_{2}H_{6(g)}}^{\circ}$ is $........... kJ \ mol^{-1}$ $(Nearest \ integer)$.