CHEMISTRY · Single correct · A Level · Chemistry · Amount of substance · Amount of substance
Problem
Which of the following best explains why, at very low temperatures, the measured pressure of a confined real gas is often lower than the pressure predicted by the ideal gas law for the same amount of substance, volume, and temperature?
(a) Because some molecules liquefy and adhere to the container walls, the number of gas-phase particles decreases, lowering the measured pressure.
(b) Because the finite volume of the molecules effectively reduces the free volume of the container, the frequency of collisions with the walls decreases, lowering the pressure.
(c) Because attractive intermolecular forces slow molecules just before they strike the walls, both the frequency and momentum of collisions decrease, lowering the pressure.
(d) Because collisions between molecules and the container walls become inelastic at low temperature, kinetic energy is lost in each collision, producing a lower pressure than predicted.