$S + \frac{3}{2} O_2 \to SO_3 + 2x \ kcal$
$SO_2 + \frac{1}{2} O_2 \to SO_3 + y \ kcal$
Find out the heat of formation of $SO_2$.

The bond dissociation enthalpies of $H_2, Cl_2$ and $HCl$ are $434, 242$ and $431 \, kJ/mol$ respectively. The enthalpy of formation of $HCl$ is ..... $kJ/mol$.

Explain the bond enthalpy.

Calculate the enthalpy change for the reaction $H_{2(g)} + Br_{2(g)} \rightarrow 2HBr_{(g)}$ in $kJ$. The bond energies of $H-H$,$Br-Br$,and $H-Br$ are $435$,$192$,and $364 \, kJ \, mol^{-1}$ respectively.

Enthalpy is an extensive property. In general,if enthalpy of an overall reaction $A \to B$ along one route is $\Delta_r H$ and $\Delta_r H_1, \Delta_r H_2, \Delta_r H_3, \dots$ represent enthalpies of intermediate reactions leading to product $B$. What will be the relation between $\Delta_r H$ for overall reaction and $\Delta_r H_1, \Delta_r H_2, \Delta_r H_3, \dots$ etc. for intermediate reactions?

The standard heat of formation,in $kcal / mol$ of $Ba^{2+}$ is
[Given : standard heat of formation of $SO_4^{2-}$ ion $(aq) = -216 \ kcal / mol$,
Standard heat of crystallisation of $BaSO_{4(s)} = -4.5 \ kcal / mol$,standard heat of formation of $BaSO_{4(s)} = -349 \ kcal / mol$]