The bond enthalpies of heavy hydrogen $(D-D)$,oxygen $(O=O)$,and heavy water $(D-O)$ are $+400$,$+498$,and $+490 \ kJ \ mol^{-1}$,respectively. The $\Delta_{r} H^{\circ}$ of the reaction to produce $D_2O$ is:

Combustion of $1$ $mol$ of benzene is expressed as:
$C_6H_{6(l)} + \frac{15}{2} O_{2(g)} \rightarrow 6CO_{2(g)} + 3H_2O_{(l)}$
The standard enthalpy of combustion of $2$ $mol$ of benzene is $-x$ $kJ$.
$x = . . . . . . . . . .$
$(1)$ Standard enthalpy of formation of $1$ $mol$ of $C_6H_{6(l)}$ is $48.5$ $kJ \ mol^{-1}$.
$(2)$ Standard enthalpy of formation of $1$ $mol$ of $CO_{2(g)}$ is $-393.5$ $kJ \ mol^{-1}$.
$(3)$ Standard enthalpy of formation of $1$ $mol$ of $H_2O_{(l)}$ is $-286$ $kJ \ mol^{-1}$.

The $\Delta H_f^o$ values for $ICl_{(g)}$,$Cl_{(g)}$,and $I_{(g)}$ are $17.57$,$121.34$,and $106.96 \, J \, mol^{-1}$ respectively. What is the bond dissociation energy of the $I-Cl$ bond in $J \, mol^{-1}$?

What will be the amount of heat evolved by burning $0.4 \ mol$ of methane? (Given heats of formation of $CH_4$,$CO_2$,and $H_2O$ are $-75$,$-400$,and $-240 \ kJ \ mol^{-1}$ respectively) ..... $kJ$

"The quantity of heat which must be supplied to decompose a compound into its elements is equal to the heat evolved during the formation of that compound from the elements." This statement is known as

The enthalpy of atomization of $PH_3(g)$ is $228 \, kcal \, mol^{-1}$ and that of $P_2H_4(g)$ is $355 \, kcal \, mol^{-1}$. The $P-P$ bond energy (in $kcal \, mol^{-1}$) is: