The standard enthalpy of formation of liquid water at $25^{\circ} C$ is approximately:
$H_{2(g)} + \frac{1}{2} O_{2(g)} \longrightarrow H_2O_{(l)}$

What will be the amount of heat evolved by burning $0.4 \ mol$ of methane? (Given heats of formation of $CH_4$,$CO_2$,and $H_2O$ are $-75$,$-400$,and $-240 \ kJ \ mol^{-1}$ respectively) ..... $kJ$

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

Based on the following thermochemical equations,find the value of $x$ in $kJ$.
$(i) \ H_2O_{(g)} + C_{(s)} \to CO_{(g)} + H_{2(g)} ; \Delta H = 131 \ kJ$
$(ii) \ CO_{(g)} + \frac{1}{2} O_{2(g)} \to CO_{2(g)} ; \Delta H = -282 \ kJ$
$(iii) \ H_{2(g)} + \frac{1}{2} O_{2(g)} \to H_2O_{(g)} ; \Delta H = -242 \ kJ$
$(iv) \ C_{(s)} + O_{2(g)} \to CO_{2(g)} ; \Delta H = -x \ kJ$

Which of the following reactions satisfies the following conditions?
$(a)$ Heat of combustion reaction
$(b)$ Heat of formation reaction
$(c)$ An exothermic reaction
$(d)$ Not a neutralization reaction

Calculate the enthalpy change of the reaction for $H_2(g) + Cl_2(g) \rightarrow 2HCl(g)$, given the bond energies (in $\text{kJ mol}^{-1}$): $H-H = 436$, $Cl-Cl = 242$, $H-Cl = 431$.