Which of the following is the correct mathematical expression for the first law of thermodynamics?

$A$ gas expands from a volume of $1 \text{ dm}^3$ to $1.25 \text{ dm}^3$ against a constant external pressure of $1 \text{ bar}$. Calculate the change in internal energy $(\Delta U)$ if $150 \text{ J}$ of heat is supplied to the system. (in $\text{ J}$)

During the melting of an ice slab at $273 \ K$ and $1 \ atm$ pressure:

$A$ heat engine absorbs heat $Q_1$ at temperature $T_1$ and heat $Q_2$ at temperature $T_2$. Work done by the engine is $(Q_1 + Q_2)$. This data

For water $\Delta_{vap} H = 41 \ kJ \ mol^{-1}$ at $373 \ K$ and $1 \ bar$ pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water,the internal energy change during evaporation of water is $...... \ kJ \ mol^{-1}$.
[Use: $R = 8.3 \ J \ mol^{-1} \ K^{-1}$]

One mole of an ideal gas at $27^oC$ is allowed to expand reversibly and adiabatically. If the work done by the system is $3 \, kJ$,then the final temperature of the gas will be ......$K$. (Given: $C_v = 20 \, J/K \cdot mol$)