Question

A semipermeable membrane allows a larger molecule to pass through but prevents the smaller one.
(a)True
(b)False

Answer 1

A semipermeable membrane doesn't allow larger molecules; according to the concentration gradient it will only allow the dissolved molecules and water to pass through and the chemical nature of the substances.

Complete answer:
A phenomenon that occurs through a semipermeable membrane where pure water flows from a dilute solution to a higher concentrated solution is known as osmosis. The meaning of a semi-permeable membrane is that this membrane will allow small molecules and ions to pass through it but acts as a barrier to larger molecules or dissolved substances. For a better understanding, we can assume that a semipermeable membrane is placed between two compartments in a tank and the membrane is permeable to water, but not to salt. If in one compartment we place a salt solution and pure water solution in the other one, to reach equilibrium the system will try to have the same concentration on both sides of the membrane, and for water, the only possible way to do this is to pass it from the pure water compartment to the saltwater compartment. At this stage, as water passes to the salt solution through the membrane, the level of liquid in the saltwater compartment will rise until enough pressure is generated to stop the osmosis. The osmotic pressure is such a kind of pressure that is equivalent to a force that the osmosis seems to exert in trying to equalize concentrations on both sides of the membrane.

Additional Information: When the molecules move from a region of higher concentration to a region of lower concentration is called diffusion and osmosis is a special case of diffusion in which the molecules are water and across a semipermeable membrane their concentration gradient occurs. The membrane with semi-These two processes diffusion and osmosis will continue until equilibrium is reached and also thermodynamically favorable. If sufficient pressure to the membrane is applied, the process of osmosis can be changed(slowed, stopped, or even reversed) from the concentrated side of the membrane. Another process is. e the reverse osmosis where the movement of the water molecule occurs against the concentration gradient occurs from lower concentration to higher concentration. For a good illustration, we can imagine a semipermeable membrane with fresh water on one side and a concentrated aqueous solution on the other side. The freshwater will cross the membrane to dilute the concentrated solution if normal osmosis takes place and if reverse osmosis occurs, the pressure will be exerted across the membrane on the water molecules with the concentrated solution to force to the fresh waterside.
So, the correct answer is,’ false’.

Note: The osmotic pressure is applied to the high concentration if pressure greater than the direction of water flow through the membrane can be reversed, that is called reverse osmosis. It can be noted that since the membrane is not permeable to salt, this reversed flow produces pure water from the salt solution.