When $6.0 \ g$ of graphite reacts with dihydrogen to give methane gas,$37.4 \ kJ$ of heat is liberated. What is the standard enthalpy of formation of $CH_{4(g)}$?

The reaction for the formation of $NaCl$ is:

What is the standard $N \equiv N$ bond enthalpy from the following reaction? $N_{2(g)} + 3H_{2(g)} \longrightarrow 2NH_{3(g)} \quad \Delta H^{\circ} = -83 \ kJ$
Given: $(\Delta H^{\circ}_{(H-H)} = 435 \ kJ \text{ mol}^{-1}, \Delta H^{\circ}_{(N-H)} = 389 \ kJ \text{ mol}^{-1})$

$XeF_{2(g)} + H_{2(g)} \to 2HF_{(g)} + Xe_{(g)}$,$\Delta H^o = -430 \ kJ$
Bond energy:
$H-H = 435 \ kJ/mol$
$H-F = 565 \ kJ/mol$
Calculate the average bond energy of the $Xe-F$ bond in $kJ/mol$.

Which of the following is an example of an endothermic reaction?

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