Given that:
$2C_{(s)} + 2O_{2(g)} \to 2CO_{2(g)}$; $\Delta H = -787 \ kJ$
$H_{2(g)} + \frac{1}{2} O_{2(g)} \to H_2O_{(l)}$; $\Delta H = -286 \ kJ$
$C_2H_{2(g)} + \frac{5}{2} O_{2(g)} \to 2CO_{2(g)} + H_2O_{(l)}$; $\Delta H = -1301 \ kJ$
Calculate the heat of formation of acetylene $(C_2H_{2(g)})$ in $kJ$.

The heat of formation of methane $C_{(s)} + 2H_{2(g)} \to CH_{4(g)}$ at constant pressure is $-18500 \ cal$ at $25 \ ^oC$. The heat of reaction at constant volume would be (in $cal$)

Calculate $\Delta H^{\circ}$ for the reaction,$Na_2O_{(s)} + SO_{3(g)} \longrightarrow Na_2SO_{4(s)}$ given the following:
$(A) \ Na_{(s)} + H_2O_{(l)} \longrightarrow NaOH_{(s)} + \frac{1}{2} H_{2(g)} \quad \Delta H^{\circ} = -146 \ kJ$
$(B) \ Na_2SO_{4(s)} + H_2O_{(l)} \longrightarrow 2NaOH_{(s)} + SO_{3(g)} \quad \Delta H^{\circ} = +418 \ kJ$
$(C) \ 2Na_2O_{(s)} + 2H_{2(g)} \longrightarrow 4Na_{(s)} + 2H_2O_{(l)} \quad \Delta H^{\circ} = +259 \ kJ$

Define thermochemical equations and explain the conventions used in them.

Given the following data:

Reaction	Energy Change (in $kJ$)
$Li_{(s)} \to Li_{(g)}$	$161$
$Li_{(g)} \to Li^{+}_{(g)}$	$520$
$\frac{1}{2} F_{2(g)} \to F_{(g)}$	$77$
$F_{(g)} + e^- \to F^{-}_{(g)}$	(Electron gain enthalpy)
$Li^{+}_{(g)} + F^{-}_{(g)} \to LiF_{(s)}$	$-1047$
$Li_{(s)} + \frac{1}{2} F_{2(g)} \to LiF_{(s)}$	$-617$

Based on the data provided,the value of electron gain enthalpy of fluorine would be $kJ\ mol^{-1}$.

Enthalpy of a compound is equal to its