Question

Semi permeable membrane is that which permits the passage of:
(A) Solute molecules only
(B) Solvent molecules only
(C) Solvent and solute molecules both
(D) Neither solute, nor solvent molecules

Answer 1

Hint: The semi permeable membrane allows only the ions to pass through it from the region of lower concentration to the region of higher concentration. The movement depends on various factors like temperature, pressure, etc.

Complete answer:
-Permeability is defined as the ability of a substance to pass through a given membrane. On the basis of permeability the membranes are divided into following 4 types:

1) Freely permeable membrane: this membrane allows various substances such as water, ions, solvents and solute to pass through it freely.
Example: cell wall in plants.

2) Impermeable membrane: This type of membrane does not allow any sort of movement of any substance through it.
Example: cutinized cell wall.

3) Semi permeable membrane: This membrane allows only the solvent molecules to pass through it and not the solute particles.
Example: egg membrane, parchment membrane.

4) Selectively permeable membrane: This membrane allows only some selective molecules of solute and solvents to pass through it. Some molecules move rapidly through it while some move slowly and some do not pass through it.
Example: tonoplast, cellophane.

-Thus now we can say that semi permeable membrane is a type of synthetic or biological, polymeric membrane which allows only some molecules or ions to pass through it via diffusion or facilitated diffusion or passive transport or active transport.
-The rate with which the ions will pass through it will depend on the pressure, concentration and temperature of the solutes and the permeability of this membrane to the respective ions.
-It allows the solvent to pass through it from the region of lower concentration to higher concentration so that the concentration becomes equal on both sides of the membrane.
But it does not allow the solute molecules to move from higher concentration to lower concentration at all.

So, the correct answer is “Option B”.

Note:Semi permeable membranes are principally used in water purification and desalination processes. It also has some chemical applications like fuel cells and batteries. A TFC material is a type of semipermeable membrane formed with molecular sieve in the form of a 2 or more layer system.