The enthalpy of neutralization of $NaOH$ by $HCl$ is $-55.84 \, kJ/mol$ and that of $NH_4OH$ by $HCl$ is $-51.34 \, kJ/mol$. The enthalpy of ionization of $NH_4OH$ is ..... $kJ/mol$.

Fill in the blanks:
$(i)$ The enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states is called the ....... of that compound.
$(ii)$ The total heat change in a chemical reaction is equal to the algebraic sum of the heat changes of the individual steps of the reaction. This law was given by .......... .
$(iii)$ $A$ process during which there is no exchange of heat between the system and the surroundings is called an ........... process.

The heat of neutralization of a strong acid and a weak base is:

The heat of combustion of acetaldehyde to carbon dioxide and water is $-1172 \ kJ \ mol^{-1}$. Calculate the amount of heat liberated when $66 \ g$ of acetaldehyde is completely oxidised. (Atomic mass: $C=12, H=1, O=16$) (in $kJ$)

Explain the bond enthalpy.

Given that the molar combustion enthalpies of benzene,cyclohexane,and hydrogen are $x, y$,and $z$ respectively,the molar enthalpy of hydrogenation of benzene to cyclohexane is