The enthalpy change for the reaction,$C_{2}H_{6(g)} \to 2C_{(g)} + 6H_{(g)}$ is $X \ kJ$. The bond energy of $C-H$ bond is :-

The standard heat of formation $\left(\Delta_{f} H_{298}^{0}\right)$ of ethane in $kJ/mol$,if the heat of combustion of ethane,hydrogen and graphite are $-1560$,$-286$,and $-393.5 \; kJ/mol,$ respectively is ........... $kJ/mol$.

Average bond enthalpy of water is $464.5 \text{ kJ mol}^{-1}$. If the energy required to break the first $O-H$ bond is $502 \text{ kJ mol}^{-1}$,how much energy per mol is required to break the second $O-H$ bond?

Calculate the enthalpy of formation of ethylene $(C_2H_4)$ from the following data:
$(I)$ $C_{\text{(graphite)}} + O_{2(g)} \longrightarrow CO_{2(g)}$; $\Delta H = -393.5 \ kJ$
$(II)$ $H_{2(g)} + \frac{1}{2} O_{2(g)} \longrightarrow H_2O_{(l)}$; $\Delta U = -256.2 \ kJ$
$(III)$ $C_2H_{4(g)} + 3 O_{2(g)} \longrightarrow 2 CO_{2(g)} + 2 H_2O_{(l)}$; $\Delta H = -1410.8 \ kJ$ (in $kJ$)

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

Consider the following processes:

Process	$\Delta H \ (kJ/mol)$
$I. \ \frac{1}{2} A \rightarrow B$	$+150$
$II. \ 3B \rightarrow 2C + D$	$-125$
$III. \ E + A \rightarrow 2D$	$+350$

For $B + D \rightarrow E + 2C, \Delta H$ will be ............. $kJ/mol$