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 $kcal$.

Calculate $\Delta S_{total}$ for the following reaction at $300 \ K$.
$NH_4NO_{3(s)} \longrightarrow NH_4^+{(aq)} + NO_3^-{(aq)}$ $(\Delta H = 28.1 \ kJ \ mol^{-1}, \Delta S_{sys} = 108.7 \ J \ K^{-1} \ mol^{-1})$

Enthalpy of fusion and enthalpy of vaporization for water respectively are $6.01 \ kJ \ mol^{-1}$ and $45.07 \ kJ \ mol^{-1}$ at $0^{\circ}C$. What is enthalpy of sublimation at $0^{\circ}C$?

Calculate $\Delta H$ when $2 \ moles$ of solid benzoic acid undergo complete combustion at $300 \ K$ if $C_6H_5COOH_{(s)} + \frac{15}{2} O_{2(g)} \rightarrow 7CO_{2(g)} + 3H_2O_{(l)}$,$\Delta U_{reaction} = -750 \ kJ/mole$ [$R = 8 \ J/mole \cdot K$].

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

If water vapour is assumed to be a perfect gas,the molar enthalpy change for the vaporisation of $1 \ mol$ of water at $1 \ bar$ and $100^{\circ} C$ is $41 \ kJ \ mol^{-1}$. Calculate the internal energy change when $1 \ mol$ of water is vaporised at $1 \ bar$ pressure and $100^{\circ} C$.