When the aqueous solution of $0.5 \, mole$ of $HNO_3$ is mixed with $0.3 \, mole$ of $OH^{-}$ solution,what will be the liberated heat in $kJ$? (Enthalpy of neutralization is $= 57.1 \, kJ \, mol^{-1}$)

Calculate the heat of reaction for the process: $NH_3(g) + HCl(g) \rightarrow NH_4Cl(s)$ given the following data:
$(i)$ $NH_3(g) + aq \rightarrow NH_3(aq)$,$\Delta H = -8.4 \, Kcal$
$(ii)$ $HCl(g) + aq \rightarrow HCl(aq)$,$\Delta H = -17.3 \, Kcal$
$(iii)$ $NH_3(aq) + HCl(aq) \rightarrow NH_4Cl(aq)$,$\Delta H = -12.5 \, Kcal$
$(iv)$ $NH_4Cl(s) + aq \rightarrow NH_4Cl(aq)$,$\Delta H = +3.9 \, Kcal$ (in $, Kcal$)

If for the reaction $CCl_{4(g)} \rightarrow C_{(g)} + 4Cl_{(g)}$ the following data is given:
$\Delta_{vap} H^{\theta} (CCl_{4(l)}) = 30 \ kJ \ mol^{-1}$
$\Delta_{f} H^{\theta} (CCl_{4(l)}) = -136.0 \ kJ \ mol^{-1}$
$\Delta_{a} H^{\theta} (C_{(s)}) = 714.0 \ kJ \ mol^{-1}$
$\Delta_{a} H^{\theta} (Cl_{2(g)}) = 242.0 \ kJ \ mol^{-1}$
Calculate the mean bond enthalpy of $C-Cl$ in $CCl_{4(g)}$.

$S_{(g)} + \frac{3}{2} O_{2(g)} \rightarrow SO_{3(g)} + 2x \ kcal$
$SO_{2(g)} + \frac{1}{2} O_{2(g)} \rightarrow SO_{3(g)} + y \ kcal$
The heat of formation of $SO_{2(g)}$ is given by :

For which of the following reactions will the value of $\Delta H$ be positive?

What is bond enthalpy? Explain bond enthalpy in polyatomic molecules like $H_2O$.