Question

The spontaneous flow of the solvent through a semipermeable membrane from a pure solvent to a solution or from a dilute solution to a concentrated solution is called osmosis. The phenomenon of osmosis can be demonstrated by taking two eggs of the same size. In an egg, the membrane below the shell and around the egg material is semipermeable. The outer hard shell can be removed by putting the egg in dilute hydrochloric acid. After removing the hard shell, one egg is placed in distilled water and the other in a saturated salt solution. After some time, the egg placed in distilled water swells up while the egg placed in salt solution shrinks. The external pressure applied to stop the osmosis is termed as osmotic pressure (a colligative property). Reverse osmosis takes place when the applied external pressure becomes larger than the osmotic pressure.
(a) Define reverse osmosis. Name one SPM which can be used in the process of reverse osmosis.

Hint:

Reverse osmosis is the process of forcing solvent through a semipermeable membrane from a concentrated solution to a diluted one, by applying pressure greater than the osmotic pressure. It’s widely used in water purification.

Answer 1

Reverse osmosis is a process in which solvent moves from a solution with higher concentration to a solution with lower concentration through a semipermeable membrane, but this process occurs when external pressure is applied that exceeds the osmotic pressure. This reverses the natural osmotic flow. An example of a semi-permeable membrane (SPM) used in reverse osmosis is cellulose acetate.