The heats of combustion $\Delta H$ of $CH_4$,$C_2H_6$,$C_2H_4$,and $C_2H_2$ gases are $-212.8$,$-373.0$,$-337.0$,and $-310.5 \ kcal$ respectively at the same temperature. Which of these gases is the best fuel?

The $C_p$ of an ideal gas is $10.314 \ J \ mol^{-1} \ K^{-1}$. One mole of this gas is expanded against a constant pressure of $p \ atm$. The change in temperature during expansion is $1.0 \ K$. The values of $q$ (in $J$) and $\Delta H$ (in $J \ mol^{-1}$) are respectively

Consider the $P-V$ (pressure-volume) diagram given below,where an ideal gas is reversibly converted from state $X$ to state $Y$. Among the following,which is the correct $T-S$ (temperature-entropy) diagram corresponding to this process?

Match the following items in List-$I$ with their corresponding expressions in List-$II$.

List-$I$	List-$II$
$A$. At constant volume the change in internal energy of a system	$I$. $W = -2.303 nRT \log \frac{V_f}{V_i}$
$B$. Isothermal irreversible change	$II$. $W_{adiabatic} = \Delta U$
$C$. Isothermal reversible change	$III$. $q_V = \Delta U$
$D$. Adiabatic change	$IV$. $W = -p_{ex} (V_f - V_i)$
	$V$. $\Delta U = \Delta H - \Delta nRT$

The enthalpy of sublimation of $I_{2(s)}$ is $57.3 \, kJ \, mol^{-1}$ and the enthalpy of fusion is $15.5 \, kJ \, mol^{-1}$. The enthalpy of vaporization of $I_2$ is ..................... $kJ \, mol^{-1}$. (in $.8$)

The heat associated with the combustion of liquid benzene at constant volume is $-3268 \ kJ \ mol^{-1}$. Calculate the change in enthalpy when this reaction occurs at $300 \ K$ $(R = 8.314 \ J \ K^{-1} \ mol^{-1})$.