Diffusion in a gas is much faster than in a liquid, as evidenced by this.

The force of interaction between molecules in a liquid state is greater than the force of interaction between molecules in a gaseous state.
Gas molecules can freely move throughout the entire volume of the vessel.
Liquid molecules vibrate about an equilibrium position and can only jump to an adjacent equilibrium position. Molecules can only swap in neighboring places.
Therefore, in gases, the molecules of one substance freely penetrate between the molecules of another substance; in liquids, this process takes more time.