For the reaction $X_2O_{4(g)} \to 2XO_{2(g)}$,given $\Delta U = 2.1 \, kcal$ and $\Delta S = 20 \, cal \, K^{-1}$ at $300 \, K$. Calculate $\Delta G$ in $kcal$.

The standard molar heat of formation of ethane,$CO_2$,and water $(l)$ are respectively $-21.1$,$-94.1$,and $-68.3 \ kcal$. The standard molar heat of combustion of ethane will be $kcal$.

Match the thermodynamic processes given under Column $I$ with the expression given under Column $II$:

Column $I$	Column $II$
$A$. Freezing of water at $273 \ K$ and $1 \ atm$	$P$. $q=0$
$B$. Expansion of $1 \ mol$ of an ideal gas into a vacuum under isolated conditions	$Q$. $w=0$
$C$. Mixing of equal volumes of two ideal gases at constant temperature and pressure in an isolated container	$R$. $\Delta S_{sys} < 0$
$D$. Reversible heating of $H_{2(g)}$ at $1 \ atm$ from $300 \ K$ to $600 \ K$,followed by reversible cooling to $300 \ K$ at $1 \ atm$	$S$. $\Delta U=0$
	$T$. $\Delta G=0$

Arrange the following in order of magnitude of work done by the system / on the system at constant temperature:
$(a)$ $|w_{reversible}|$ for expansion in infinite stage.
$(b)$ $|w_{irreversible}|$ for expansion in single stage.
$(c)$ $|w_{reversible}|$ for compression in infinite stage.
$(d)$ $|w_{irreversible}|$ for compression in single stage.
Choose the correct answer from the options given below:

For isothermal expansion of an ideal gas,the correct combination of the thermodynamic parameters will be

$A$ thermodynamic cycle in the pressure $(p)-$ volume $(V)$ plane is given below. $A B$ and $C D$ are isothermal processes while $B C$ and $D A$ are adiabatic processes. The same cycle in the temperature $(T) -$ entropy $(S)$ plane is