The heat of neutralisation of a strong acid and a strong alkali is $57.0 \ kJ \ mol^{-1}$. The heat released when $0.5 \ mol$ of $HNO_3$ solution is mixed with $0.2 \ mol$ of $KOH$ is: (in $kJ$)

Given that $\Delta H_f(H) = 218 \ kJ/mol$, express the $H-H$ bond energy in $kcal/mol$.

Identify the $INVALID$ equation.

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:

Calculate the $\Delta_fH^{\circ}$ of $N_2H_{4(g)}$ given the following bond energies:
$B.E.(N-N) = 159 \ kJ \ mol^{-1}$
$B.E.(H-H) = 436 \ kJ \ mol^{-1}$
$B.E.(N \equiv N) = 941 \ kJ \ mol^{-1}$
$B.E.(N-H) = 398 \ kJ \ mol^{-1}$

Given two processes:
$\frac{1}{2} P_{4(s)} + 3 Cl_{2(g)} \to 2 PCl_{3(l)} \;; \Delta H = -635 \ kJ$
$PCl_{3(l)} + Cl_{2(g)} \to PCl_{5(s)} \;; \Delta H = -137 \ kJ$
The value of the heat of formation of $PCl_{5(s)}$ is ...... $kJ \ mol^{-1}$.