JEE Main · 2020 · 04 Sep 2020 · Shift 2 · Chemical Thermodynamics

Five moles of an ideal gas at 1 bar and 298 K is expanded into vacuum to double the volume. The work done is :

Answer: (C)

Solution

When a gas expands into a vacuum the external pressure is zero, and the work done against the surroundings is

W = - P_{ext} Δ V

. With

P_{ext} = 0

this is zero whatever the change in volume, so a free expansion does no work and the work done is zero.

JEE Main · 2020 · 04 Sep 2020 · Shift 2 · Single correct option