One mole of an ideal gas at 300 K is expanded isothermally from 1 L to 10 L volume. $$\Delta$$U for this process is :

(Use R = 8.314 J k^$$-$$1 mol^$$-$$1)

A vessel contains 3.2 g of dioxygen gas at STP (273.15 K and 1 atm pressure). The gas is now transferred to another vessel at constant temperature, where pressure becomes one third of the original pressure. The volume of new vessel in L is : (Given : molar volume at STP is 22.4 L)

Which of the following p-V curve represents maximum work done?