Total enthalpy change for freezing of $1 \ mol$ of water at $10^{\circ} C$ to ice at $-10^{\circ} C$ is $..........$ (Given : $\Delta_{fus} H = x \ kJ / mol$,$C_{p}[H_2O_{(l)}] = y \ J \ mol^{-1} \ K^{-1}$,$C_{p}[H_2O_{(s)}] = z \ J \ mol^{-1} \ K^{-1}$)

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?

$10 \, mol$ of an ideal gas expands isothermally and reversibly from a pressure of $10 \, atm$ to $1 \, atm$ at $300 \, K$. What is the largest mass (in $kg$) which can be lifted through a height of $100 \, m$ by the energy obtained in this process (in $, kg$)?

$2.2 \, g$ of nitrous oxide $(N_{2}O)$ gas is cooled at a constant pressure of $1 \, atm$ from $310 \, K$ to $270 \, K$ causing the compression of the gas from $217.1 \, mL$ to $167.75 \, mL$. The change in internal energy of the process,$\Delta U$ is $-x \, J$. The value of $x$ is $....$ [nearest integer] (Given: atomic mass of $N = 14 \, g \, mol^{-1}$ and of $O = 16 \, g \, mol^{-1}$. Molar heat capacity of $N_{2}O$ is $100 \, J \, K^{-1} \, mol^{-1}$)

$\Delta H_f^o$ of water is $-285.5\, kJ\, mol^{-1}$. If enthalpy of neutralisation of monoacidic strong base is $-57.3\, kJ\, mol^{-1}$,$\Delta H_f^o$ of $OH^{-}$ ion will be $.....\, kJ\, mol^{-1}$.

The heat of combustion $\left(kJ \ mol^{-1}\right)$ is highest for