On combustion,carbon forms two oxides $CO$ and $CO_2$. The heat of formation of $CO_2$ gas is $-94.3 \, kcal$ and that of $CO$ is $-26.0 \, kcal$. The heat of combustion of carbon is.......$kcal$.

With the help of the following data,find out the change in heat content for the reaction in $kJ$:
$C_2H_{4(g)} + H_{2(g)} \to C_2H_{6(g)}$

Bond	Bond energy $(kJ \ mol^{-1})$
$C-H$	$413$
$C-C$	$348$
$C=C$	$610$
$H-H$	$436$

Given:
$C + 2S \to CS_2 ; \Delta H_f^o = +117.0 \, kJ \, mol^{-1} \dots (1)$
$C + O_2 \to CO_2 ; \Delta H_f^o = -393 \, kJ \, mol^{-1} \dots (2)$
$S + O_2 \to SO_2 ; \Delta H_f^o = -297 \, kJ \, mol^{-1} \dots (3)$
The heat of reaction for $CS_2 + 3O_2 \to CO_2 + 2SO_2$ is:
.....$kJ \, mol^{-1}$

$A$,$B$,$C$ and $D$ are some compounds. The enthalpy of formation of $A_{(g)}$,$B_{(g)}$,$C_{(g)}$ and $D_{(g)}$ is $9.7, -110, 81$ and $-393 \ kJ \ mol^{-1}$ respectively. What is $\Delta_r H$ (in $kJ \ mol^{-1}$) for the given reaction?
$A_{(g)} + 3B_{(g)} \longrightarrow C_{(g)} + 3D_{(g)}$

For which of the following reactions will the value of $\Delta H$ be positive?

The standard enthalpy of formation $(\Delta_f H^o_{298})$ for methane,$CH_4$ is $-74.9 \ kJ \ mol^{-1}$. In order to calculate the average energy given out in the formation of a $C-H$ bond from this,it is necessary to know which one of the following?