Question

A non-electrolyte solution containing 21.6 g of an unknown solute in 0.2 L of water has an osmotic pressure of 1.47 × 106 Pa at 298 K. What is the identity of the solute molecule?

(A) CaCl2 (111 g mol–1) (B) sucrose (507 g mol–1) (C) vitamin A (286 g mol–1) (D) fructose (182 g mol–1) (E) urea (60.0 g mol–1)

Answer 1

1.47*10^6 Pa = 14.51 atm

Osmotic pressure (π) = concentration * gas constant * temperature

=> 14.51 = concentration * 0.082 * 298

Concentration = 0.594

Molarity = moles / volume ( in litre )

= 0.594 = moles / 0.2

Moles = 0.1188

Molar mass = mass / moles

= 21.6 / 0.1188

= 181.82 grams / mol

It is fructose because it is non electrolyte and its mass has 182 grams / mole

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