Which of the following reactions is endothermic?

The heat of combustion of carbon is $-94 \ kcal$ at $1 \ atm$ pressure. The internal energy of $CO_2$ is .... $kcal$.

Consider the reaction $4NO_2(g) + O_2(g) \rightarrow 2N_2O_5(g)$, $\Delta_rH = -111 \ kJ$. If $N_2O_5(s)$ is formed instead of $N_2O_5(g)$, what will be the value of $\Delta_rH$ in $kJ$? (Given: $\Delta H_{sub} = 54 \ kJ \ mol^{-1}$ for $N_2O_5$)

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

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

The heat of combustion of carbon is $-393.5 \ kJ / mol$. The heat released upon the formation of $35.2 \ g$ of $CO_{2}$ from carbon and oxygen gas is

One mole of ethanol $(l)$ was completely burnt in oxygen to form $CO_{2(g)}$ and $H_2O_{(l)}$. What is the $\Delta_r H^{\ominus}$ (in $kJ \ mol^{-1}$) for this reaction?
(The standard enthalpy of formation $(\Delta_f H^{\ominus})$ of $C_2H_5OH_{(l)}$,$CO_{2(g)}$ and $H_2O_{(l)}$ is respectively $-277, -393$ and $-286 \ kJ \ mol^{-1}$.)