Real Gases -- Kaplan FL4 PS

[Dr Gerrard]

42. A real gas is compressed at constant temperature
from an initial pressure of P0 and an initial volume of
V0 to a final volume of (1/2)V0. Its final pressure is:

A. more than 2P0.
B. 2P0.
C. less than 2P0.
D. indeterminate, depending on the precise initial
conditions.

I said C. However, the answer is D. Their explanation makes sense, but it goes against what EK says.

EK says that a real gas has a smaller pressure than an ideal gas. Do they acknowledge that it is only the case in some conditions?

Kaplan says D, because a real gas has a smaller volume then an ideal gas, so it must have a greater pressure to make up for it.

Thus, the smaller volume makes up a greater pressure, while the intermolecular forces cause a smaller pressure.

Do we really have to take into consideration the first one though?

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[RogueUnicorn]

42. A real gas is compressed at constant temperature
from an initial pressure of P0 and an initial volume of
V0 to a final volume of (1/2)V0. Its final pressure is:

A. more than 2P0.
B. 2P0.
C. less than 2P0.
D. indeterminate, depending on the precise initial
conditions.

I said C. However, the answer is D. Their explanation makes sense, but it goes against what EK says.

EK says that a real gas has a smaller pressure than an ideal gas. Do they acknowledge that it is only the case in some conditions?

Kaplan says D, because a real gas has a smaller volume then an ideal gas, so it must have a greater pressure to make up for it.

Thus, the smaller volume makes up a greater pressure, while the intermolecular forces cause a smaller pressure.

Do we really have to take into consideration the first one though?

real gasses have two additional considerations: actual volume of the gas particle (which will increase the volume) and intermolecular attraction (which decreases pressure) the precise interplay of this is given by the van der Waals equation of state (out of scope for MCAT but the concept is not). These coefficients are experimental values so it's impossible to do these theoretical exercises without more data.