To solve this problem, we need to analyze the thermodynamic properties of an ideal gas undergoing irreversible expansion under isothermal conditions.$\\$Given:$\\$• The process is isothermal, meaning the temperature remains constant.$\\$• The expansion is irreversible.$\\$Let's analyze the changes in internal energy and entropy:$\\$1. Change in Internal Energy $(\Delta U): \\$For an ideal gas, the internal energy depends only on temperature. Since the process is isothermal,$\\ \Delta U = 0. \\$2. Change in Total Entropy $(\Delta S_{total}): \\$The total entropy change is the sum of the entropy change of the system and the surroundings.$\\$In an irreversible process, the total entropy change is greater than zero.$\\ \Delta S_{total} \neq 0. \\$Therefore, for an irreversible isothermal expansion of an ideal gas:$\\ \Delta U = 0, \Delta S_{total} \neq 0. \\$This corresponds to Option 3.