A 5.25% solution of a substance is isotonic with a 1.5% solution of urea ( molar mass = 60 g mol -1 ) in the same solvent. If the densities of both the solutions are assumed to be equal to 1.0 g cm -3 , molar mass of the substance will be

Question

A 5.25% solution of a substance is isotonic with a 1.5% solution of urea ( molar mass = 60 g mol -1 ) in the same solvent. If the densities of both the solutions are assumed to be equal to 1.0 g cm -3 , molar mass of the substance will be, 210 g mol -1, 90.0 g mol -1, 115.0 g mol -1, 105.0 g mol -1

MARKS App · Accepted Answer

Isotonic solutions have same osmotic pressure. π 1 = C 1 RT, π 2 = C 2 RT For isotonic solution, π 1 = π 2 π = 5 · 2 5 / M 1 0 0 × 1 0 RT = 1 · 5 / 6 0 1 0 0 × 1 0 RT 5 · 2 5 M = 1 · 5 6 0 M = 6 0 × 5 · 2 5 1 · 5 = 2 1 0 g / mole

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