Which of the following processes exhibits $\Delta U = 0$?

In an isothermal and reversible process,$1.6 \times 10^{-2} \ kg$ of $O_2$ expands from $10 \ dm^3$ to $100 \ dm^3$ at $300 \ K$. The work done in the process is: $(R = 8.314 \ J \ K^{-1} \ mol^{-1})$ (in $J$)

An ideal gas expands from $1 \times 10^{-3} \ m^{3}$ to $1 \times 10^{-2} \ m^{3}$ at $300 \ K$ against a constant external pressure of $1 \times 10^{5} \ Nm^{-2}$. The work done is:

Graphically show the total work done in an expansion when the state of an ideal gas is changed reversibly and isothermally from $(P_i, V_i)$ to $(P_f, V_f)$. With the help of a $pV$ plot,compare the work done in the above case with that carried out against a constant external pressure $P_f$.

Work done when $2 \ mol$ of an ideal gas is compressed from a volume of $5 \ m^{3}$ to $2.5 \ m^{3}$ at $300 \ K$, under a constant external pressure of $100 \ kPa$ is: (in $kJ$)

For the reaction $H_{2}F_{2(g)} \rightarrow H_{2(g)} + F_{2(g)}$,$\Delta U = -59.6 \ kJ \ mol^{-1}$ at $27^{\circ} C$. The enthalpy change for the above reaction is $(-)$ $kJ \ mol^{-1}$ [nearest integer]. Given: $R = 8.314 \ J \ K^{-1} \ mol^{-1}$.