The following thermochemical reactions are given:
$M + \frac{1}{2} O_2 \to MO + 351.4 \ kJ$ $(i)$
$X + \frac{1}{2} O_2 \to XO + 90.8 \ kJ$ $(ii)$
It follows that the heat of reaction for the following process $M + XO \rightleftharpoons MO + X$ is given by $... \ kJ$.

The standard heats of formation for $CH_4$, $C_2H_4$, and $C_3H_8$ are $-17.9$, $12.5$, and $-24.8 \ kcal/mol$ respectively. The heat of reaction $(\Delta H)$ for the reaction $CH_4 + C_2H_4 \rightarrow C_3H_8$ in $kcal$ is:

The lowest value of heat of neutralization is obtained for

The heats of combustion of carbon and carbon monoxide are $-394 \, kJ \, mol^{-1}$ and $-285 \, kJ \, mol^{-1}$ respectively. Find the heat of formation of $CO$ in $kJ \, mol^{-1}$.

The heat of formation of water is $260 \ kJ$. How much $H_2O$ is decomposed by $130 \ kJ$ of heat (in $mol$)?

Represent the potential energy / enthalpy change in the following processes graphically.
$(a)$ Throwing a stone from the ground to the roof.
$(b)$ $\frac{1}{2} H_{2(g)} + \frac{1}{2} Cl_{2(g)} \rightarrow HCl_{(g)}$
In which of the processes is the potential energy/enthalpy change a contributing factor to the spontaneity?