Question

Which of the following is correct about diffusion and osmosis?
\[(i)\] In osmosis, a semipermeable membrane is used while diffusion is without any membrane
\[(ii)\] In osmosis, movement of molecules occurs in one direction while in diffusion, movement occurs in all directions.
\[(iii)\] In osmosis, only the solvent moves while in diffusion both solute and solvent move
     \[
  1.(i){\text{ and (ii) }} \\
  {\text{2}}{\text{.(i) only}} \\
  {\text{3}}{\text{.(ii) and (iii)}} \\
  {\text{4}}{\text{. (i),(ii) and (iii) }} \\
 \]

Answer 1

Hint: Diffusion is obvious in gases and liquids, but diffusion in solids rather than of solids is more common. Diffusion rate is affected by the gradient of concentration, the size of particle, temperature and pressure.

Complete answer:
Firstly we will understand what diffusion is. The movement of molecules or ions from the region of their higher concentration to the region of their lower concentration, until the molecules are evenly distributed throughout the available space is known as diffusion. These diffusing particles create a certain pressure called diffusion pressure which is directly proportional to the number or concentration of diffusing particles. The molecules move from higher diffusion pressure to lower diffusion pressure.
The characteristics are:
\[1.\] The molecule diffuses from higher concentration to lower concentration, until equilibrium is established.
\[2.\] The diffusing molecule moves randomly along the concentration gradient.
\[3.\] The direction of movement is independent of other molecules.
Now let us understand osmosis, It is a special type of diffusion across a differentially or semipermeable membrane. Thus, the osmosis can be defined as “the passage of solvent molecules from a region of their higher concentration to a region of lower concentration through a semipermeable membrane”.it occurs spontaneously in a response to a driving force. Osmosis is driven by two factors:
\[1.\] Concentration of dissolved solute in a solution
\[2.\] Pressure gradient
Both these factors determine the chemical potential of solvent, which is the driving force of its movement. It is unidirectional.

Note:
Equilibrium is a dynamic state in which the rate of forward and backward reaction is equal.it should not be confused with steady state. Osmosis is demonstrated by simple experiments in a laboratory.one is Potato osmometer and Thistle funnel experiment.