The heat of neutralization of a strong acid by a strong base is nearly equal to

The bond energies of $H-H$ and $Cl-Cl$ are $430 \ kJ \ mol^{-1}$ and $240 \ kJ \ mol^{-1}$ respectively. If the $\Delta H_f$ (enthalpy of formation) of $HCl$ is $-90 \ kJ \ mol^{-1}$,what is the $H-Cl$ bond energy in $kJ \ mol^{-1}$?

The enthalpy change for the transition of carbon from diamond to graphite is $\Delta H = -453.5 \ \text{cal}$. What does this indicate?

The enthalpy of formation of ethane $(C_2H_6)$ from ethylene $(C_2H_4)$ by the addition of hydrogen,where the bond energies of $C-H$,$C-C$,$C=C$,and $H-H$ are $414 \ kJ/mol$,$347 \ kJ/mol$,$615 \ kJ/mol$,and $435 \ kJ/mol$ respectively,is $........$ $kJ/mol$.

State Hess's Law of Constant Heat Summation.

The calorific value of hydrogen gas is $-143 \ kJ \ g^{-1}$. The standard enthalpy of formation of $H_2O$ will be $—$