Which of the following $p-V$ curves represents the maximum work done?

For which of the following processes will the value of $\Delta H^{\circ} - \Delta G^{\circ}$ be approximately zero?

$A$ sample of argon at $1 \text{ atm}$ pressure and $300 \text{ K}$ expands reversibly and adiabatically from $1.25 \text{ dm}^3$ to $2.5 \text{ dm}^3$. Calculate the approximate enthalpy change (in $\text{J}$).
$(I)$ $C_V$ for argon is $12.48 \text{ J K}^{-1} \text{ mol}^{-1}$
$(II)$ Assume argon to be an ideal gas
$(III)$ $\Delta T = 111.5 \text{ K}$ (temperature decrease)

Calculate the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume at $27^{\circ} C$ (in $cal$)? $(R = 2 \ cal \ K^{-1} \ mol^{-1})$

An organic compound $C_xH_yO_z$ on complete combustion provides equivolume of products $CO_{2(g)}$ and $H_2O_{(g)}$,which is individually double the volume of the organic compound taken. In the process,the volume of oxygen consumed is the same as the volume of $CO_2$ produced,and the liberated heat during combustion is $500 \ kcal/mol$ at constant pressure and $500 \ K$. The formula of the organic compound and $\Delta U$ for the reaction will be:

For the reactions,$C + O_2 \to CO_2; \Delta H = -393 \ J$
$2Zn + O_2 \to 2ZnO; \Delta H = -412 \ J$