Which of the following is not an endothermic reaction?

The lowest value of heat of neutralization is obtained for

The enthalpy of $1 \ mol$ of a compound is equal to its ...... (when it is formed from its constituent elements).

When $0.5 \ g$ of sulphur is burnt to $SO_2$,$4.6 \ kJ$ of heat is liberated. What is the enthalpy of formation of sulphur dioxide in $kJ \ mol^{-1}$?

Calculate the enthalpy change for the following reaction:
$H_2C=CH_{2(g)} + H_{2(g)} \longrightarrow H_3C-CH_{3(g)}$
[The bond energies of $C-H, C-C, C=C$ and $H-H$ are $414, 347, 615$ and $435 \ kJ/mol$ respectively.] (in $kJ$)

At $25^{\circ} \text{C}$, the standard enthalpies of combustion of $H_2(g)$, cyclohexene $(C_6H_{10})$, and cyclohexane $(C_6H_{12})$ are $-241 \text{ kJ mol}^{-1}$, $-3800 \text{ kJ mol}^{-1}$, and $-3920 \text{ kJ mol}^{-1}$ respectively. Calculate the heat of hydrogenation of cyclohexene.