An ideal gas expands from a volume of 1 L to 3 L against a constant external pressure of 2 bar . If the gas absorbs 800 J of heat from the surroundings during this process, what is the change in internal energy of the system? ( 1 L bar = 100 J )

Step-by-step solution

The work done during the irreversible expansion of a gas against a constant external pressure is given by: w = -P_ ext V Given: P_ ext = 2 bar V = V₂ - V₁ = 3 L - 1 L = 2 L w = -2 bar 2 L = -4 L bar Converting to Joules: w = -4 100 J = -400 J Heat absorbed by the system, q = +800 J According to the first law of thermodynamics: U = q + w U = 800 J + (-400 J ) = 400 J Answer: 400 J