At $298 \, K$,the bond energies of $C-H$,$C-C$,$C=C$,and $H-H$ bonds are $414$,$347$,$615$,and $435 \, kJ \, mol^{-1}$ respectively. What is the enthalpy change for the reaction $H_2C=CH_{2(g)} + H_{2(g)} \rightarrow H_3C-CH_{3(g)}$ at $298 \, K$?

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 ..... $kJ \, mol^{-1}$.

At standard conditions,if the change in the enthalpy for the following reaction is $-109 \; kJ \ mol^{-1}$:
$H_{2(g)} + Br_{2(g)} \rightarrow 2HBr_{(g)}$
Given that bond energy of $H_2$ and $Br_2$ is $435 \; kJ \ mol^{-1}$ and $192 \; kJ \ mol^{-1}$,respectively,what is the bond energy (in $kJ \ mol^{-1}$) of $HBr$?

On combustion,carbon forms two oxides $CO$ and $CO_2$. The heat of formation of $CO_2$ gas is $-94.3 \, kcal$ and that of $CO$ is $-26.0 \, kcal$. The heat of combustion of carbon is.......$kcal$.

The heats of combustion of yellow phosphorus and red phosphorus are $-9.91 \, kJ$ and $-8.78 \, kJ$ respectively. The heat of transition for the conversion of yellow phosphorus to red phosphorus will be ...... $kJ$?

The total enthalpies of reactants and products are $H_R$ and $H_P$ respectively. For an exothermic reaction,which of the following is true?