How to Solve Thermodynamics Problems when a Gas Undergoes Expansion into a Vacuum – Part 1

The first law of thermodynamics states that, when energy passes into or out of a system (as work, heat, or matter), the system's internal energy changes in accordance with the law of conservation of energy.


An isothermal process means no change in temperature while an adiabatic process means no heat exchange. An expansion into a vacuum is a free expansion and an irreversible change.

Question:

2 L of an ideal gas at a pressure of 10 atm expands isothermally at 25°C into a vacuum until its total volume is 10 L. How much heat is absorbed and how much work is done in the expansion? What if the same happens under an adiabatic condition?

Solution:



Click/tap to enlarge the image

Pext = External pressure, ΔU = Change in internal energy, ΔT = Change in absolute temperature, w = Work done, ΔV = Change in volume, q = Heat

Convinced❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

Reference:
Wikipedia Contributors. Laws of thermodynamics. Wikipedia. https://en.wikipedia.org/wiki/Laws_of_thermodynamics.

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