NTA Abhyas JEE Main2020ChemistrySolutionsPractice
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
Options
- A210 g mol -1
- B90.0 g mol -1
- C115.0 g mol -1
- D105.0 g mol -1
Correct answer
A. 210 g mol -1
Step-by-step solution
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