Question

The decreasing order of diffusion is-------
(A) Gas > Solid > Liquid
(B) Liquid > Gas > Solid
(C) Solid > Liquid > Gas
(D) Gas > Liquid > Solid

Answer 1

Hint: Rate of diffusion is affected by nature of substance, concentration gradient, permeability of membrane pressure and temperature.
Order of density of different substances is gas < liquid < solid.

Complete Answer:
Diffusion is the movement of particles of different substances from the region of their high concentration, free energy or diffusion pressure to the region of their lower concentration, free energy or diffusion pressure.
Simple diffusion is a random kinetic motion of ions, particles and molecules of solid liquid and gas from their high concentration to low concentration until the equilibrium is not established. At this stage the movement of the molecules will be equal in both directions so net movement will be zero.
Diffusion is a slow process and not depends on the living system for energy. This is a non-selective process which does not have a saturation point. Diffusion of a substance is independent from the diffusion of other substances. Diffusion is a very important process to plant and other animals since it is the only means of gaseous exchange within the plant and animal body.
Density of solid is more than liquid, and the density of liquid is higher than gas. Since rate of diffusion is inversely proportional to the density of molecular substance, so rate of diffusion will be highest for gaseous state in respect to the rate of liquid and solid state.
\[\text{rate}\,\text{of diffusion }\alpha \,\,\dfrac{1}{\sqrt{\text{density of molecule}}}\]
Since the order of density is solid > liquid > gas, so the order of diffusion rate of diffusion will be gas > liquid > solid.

So the option (D) will be the correct option.

Note: osmosis is defined as the special diffusion of solvent (water in this context) from the solution of lower concentration (hypotonic) to the solution of higher concentration (hypertonic) where both the solutions are separated by a semipermeable membrane.
Diffusion of a substance is independent from the diffusion of other substances.