Question

A 1 liter sample of pure gas is found to have a lower pressure than that predicted by the ideal gas law. What is the best explanation for this observation?

1) The gas is not pure
2) The gas is at a higher temperature than expected
3) The gas is at a lower temperature than expected
4) The gas molecules are interacting with each other

Answer 1

The best explanation for a pure gas having lower pressure than predicted by the ideal gas law is due to intermolecular interactions between gas molecules, especially under high pressures or low temperatures.

Step-by-step explanation:

If a 1 liter sample of pure gas has a lower pressure than that predicted by the ideal gas law, the best explanation for this observation is that the gas molecules are interacting with each other (option 4). This deviation from ideal behavior is evident under conditions where gases are put under high pressure or at low temperatures. Particularly, at high pressures, the gas molecules are forced closer together, diminishing the empty space between them, making the volume of the particles non-negligible. Also, at lower temperatures, the kinetic energy decreases, leading to more significant attractive forces between molecules which the ideal gas law does not account for.