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Which of the following expressions is incorrect for a real gas at high pressure and room temperature?

1. Z > 1
2. Z = 1 + a/(R*T*Vₘ)
3. Z = 1 + P*b/(R*T)
4. Repulsive forces dominant

Correct answer: Z = 1 + a/(R*T*Vₘ)

Solution

At high pressure, the dominant correction comes from the finite volume of molecules (b term), giving Z = 1 + Pb/RT and Z > 1; the expression Z = 1 + a/(RTVₘ) is actually the low-pressure (large volume) correction and is incorrect here.

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