Question

What are isotonic solutions?

Answer 1

Iso means the same and tone means concentration. Osmotic pressure is directly proportional to concentration of solution at a given temperature. Two solutions having the same concentration have the same osmotic pressure.

Complete solution step by step:
-All substances are bound by membranes. These membranes have submicroscopic pores. -Small molecules like water can pass through these holes but bigger molecules like solute cannot pass through this hole.
-Membranes which have such properties are called semi permeable membranes.
-Only solvent molecules can permeate through semi permeable membranes. When a semipermeable membrane is placed between solution and solvent, solvent molecules flow through the membrane from pure solvent to solution.
-When solvent molecules move from lower concentration to higher concentration through semi permeable membranes, the process is called osmosis.
-Solvent molecule flow till equilibrium is attained. This flow of solvent molecules can be stopped by applying extra pressure.
-Pressure that will just stop the flow of solvent molecules is called osmotic pressure.
-The molecules of solvent always flow from lower concentration to higher concentration of solution.
-Osmotic pressure is excess pressure that must be applied to stop the flow of solvent molecules.
-Osmotic pressure is a colligative property, it depends on the number of solute molecules.
-Osmotic pressure is proportional to concentration of solution at given temperature.
-Two solutions with equal osmotic pressure at a given temperature are called isotonic solutions.
-No osmosis occurs between such solutions when separated by semi permeable membranes.

Note: Osmotic pressure of fluid inside the blood cell is equivalent to 0.9% of sodium chloride solution. When placed in a solution having concentration more than 0.9%, called a hypertonic solution, the blood cell will shrink. When placed in a solution having concentration less than 0.9%, called a hypotonic solution, the blood cell will swell.