4.0 L of an ideal gas is allowed to expand isothermally into vacuum until the total volume is 20 L. The amount of heat absorbed in this expansion is__________L atm.

Explanation

In a free expansion into a vacuum:

• The gas expands without doing work (no opposing pressure).
• The internal energy remains constant in an isothermal process.
• Since no work is done and internal energy doesn't change, no heat is absorbed or released.

Given

• Type of process: Isothermal expansion into a vacuum (also called free expansion).
• In a vacuum, there’s no external pressure acting on the gas.
• Work done (W) in free expansion = 0 (because no external pressure)
• For an ideal gas in an isothermal process, internal energy change (∆U) = 0 (since temperature is constant)

According to the first law of thermodynamics:

∆U = Q - W

Since ∆U = 0 and W = 0,

Q = 0

The amount of heat absorbed in this expansion is 0 L atm.