The temperature of the system decreases in an

Standard enthalpy of vaporisation $\Delta_{vap}H^o$ for water at $100\ ^oC$ is $40.66\ kJ\ mol^{-1}.$ The internal energy of vaporisation of water at $100\ ^oC$ (in $kJ\ mol^{-1}$) is ............... $kJ\ mol^{-1}$ (Assume water vapour to behave like an ideal gas)

$A$ gas occupies $1.5 \ L$ at $S.T.P.$ It is provided with $300 \ J$ of heat so that its volume becomes $2 \ L$ at a pressure of $1 \ atm$. The value of $\Delta U$ for the process is.....joule.

Calculate $\Delta U$ if $2 \ kJ$ heat is released and $10 \ kJ$ of work is done on the system. (in $kJ$)

Five moles of an ideal gas at $293 \, K$ is expanded isothermally from an initial pressure of $2.1 \, MPa$ to $1.3 \, MPa$ against a constant external pressure of $4.3 \, MPa$. The heat transferred in this process is $...... \, kJ \, mol^{-1}$. (Rounded-off to the nearest integer) $\left[\right.$ Use $R = 8.314 \, J \, mol^{-1} \, K^{-1}\left.\right]$

For the $1^{st}$ law of thermodynamics,select the correct option.