For the reaction $C_{2}H_{6} \rightarrow C_{2}H_{4} + H_{2}$,the reaction enthalpy $\Delta_{r}H = \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \, kJ \, mol^{-1}$. (Round off to the Nearest Integer). [Given: Bond enthalpies in $kJ \, mol^{-1} : C-C : 347, C=C : 611, C-H : 414, H-H : 436$]

The heat of solution of $Na_2SO_{4(s)}$ and $Na_2SO_4 \cdot 10H_2O_{(s)}$ are $-2.34 \ kJ \ mol^{-1}$ and $78.87 \ kJ \ mol^{-1}$ respectively. The heat of hydration of $Na_2SO_{4(s)}$ is:

The heat of hydrogenation of cyclohexene is $28.6 \, kcal$ and that of cyclohexadiene is slightly more than double,$(55.4 \, kcal)$. What will be the heat of hydrogenation of benzene,which contains three double bonds?

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 $kJ$)

The heat of combustion of a substance is:

The heat of combustion of carbon is $-94 \ kcal$ at $1 \ atm$ pressure. The internal energy of $CO_2$ is .... $kcal$.