Question

A solution X is prepared by dissolving three moles of glucose in one litre of water and a solution Y is prepared by dissolving 1.5 moles of sodium chloride in one litre of water. Will the osmotic pressure of X be higher, lower or equal to that of Y? Give a reason for your answer.

Answer 1

The osmotic pressure of solution X will be equal to that of solution Y.

Reason:

Osmotic pressure is given by the formula

π = iCRT

Where

i = van’t Hoff factor (number of particles the solute produces)

C = molarity

R = gas constant

T = temperature

For solution X (Glucose):

Glucose is a non-electrolyte and does not dissociate, so i = 1 Mole = 3

So, πX = 1 × 3 × R × T

= 3RT

For solution Y (NaCl):

NaCl is astrong electrolyte dissociates into, Na⁺ and Cl⁻ → i = 2

So, πX = 1 × 3 × R × T

= 3RT

Since both π_X and π_Y​ = 3RT,

The osmotic pressures in both solutions are equal.