At $25^{\circ}C$,the heats of combustion for $CH_{4(g)}$,$C_{(s)}$,and $H_{2(g)}$ are $-212.4 \, kcal$,$-94.0 \, kcal$,and $-68.4 \, kcal$ respectively. The heat of formation for $CH_{4(g)}$ in $kcal$ is:

Use the data from the table to estimate the enthalpy of formation of $CH_3CHO$.

Bond	Bond Enthalpy $(kJ \ mol^{-1})$	Enthalpy of formation $(kJ \ mol^{-1})$
$C-H$	$400$	$C(g): 700$
$C-C$	$350$	$H(g): 200$
$C=O$	$700$	$O(g): 250$

Calculate the enthalpy of formation of ethylene $(C_2H_4)$ from the following data:
$(I)$ $C_{\text{(graphite)}} + O_{2(g)} \longrightarrow CO_{2(g)}$; $\Delta H = -393.5 \ kJ$
$(II)$ $H_{2(g)} + \frac{1}{2} O_{2(g)} \longrightarrow H_2O_{(l)}$; $\Delta U = -256.2 \ kJ$
$(III)$ $C_2H_{4(g)} + 3 O_{2(g)} \longrightarrow 2 CO_{2(g)} + 2 H_2O_{(l)}$; $\Delta H = -1410.8 \ kJ$ (in $kJ$)

For which of the following reactions is the $\Delta H^o$ of the reaction equal to the $\Delta H_f^o$ of the product?

What is the standard enthalpy of reaction (in $kJ$) when two moles of $Fe_2O_{3(s)}$ react with $H_2$ gas to give $Fe$ metal? $\Delta H_f^{\circ}$ of $Fe_2O_{3(s)}$ and $H_2O_{(l)}$ are $-824.2$ and $-285.83 \ kJ \ mol^{-1}$ respectively.

Given: $S + O_2 \rightarrow SO_2 : \Delta H_1 = -298.2 \ kJ$,$SO_2 + 1/2 \ O_2 \rightarrow SO_3 : \Delta H_2 = -98.7 \ kJ$,$SO_3 + H_2O \rightarrow H_2SO_4 : \Delta H_3 = -130.2 \ kJ$,and $H_2 + 1/2 \ O_2 \rightarrow H_2O : \Delta H_4 = -287.3 \ kJ$. Calculate the heat of formation of $H_2SO_4$ in $kJ$.