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 (a) 210.0 g mol⁻¹ (b) 90.0 g mol⁻¹(c) 115.0 g mol⁻¹(d) 105.0 g mol⁻¹.
Answers
Answer:
(a) 210.0 g mol^-1 is the correct answer.
Explanation:
Isotonic solution:
Two or more solutions exerting the same osmotic pressure are called as isotonic solution.
The example of isotonic solution is given below:
0.05M urea solution and 0.05M sucrose solution are isotonic solutions as their osmotic pressure is exactly equal.
If these 2 solutions are passes through a semi permeable membrane, there is no flow of solvent in either direction.
Given data
5.25% solution of a substance is isotonic with a 1.5% solution
urea (molar mass = 60 g mol^-1
The solvent used is same solvent
Densities of both the solutions =1.0 g cm^-3,
To find:
molar mass of the substance =?
The solutions are isotonic.
Thus according to the definition,
The concentrations of the solution will be the same.
C1 = C2
5.25/M= 1.5/60 .... (Given data)
Thus by cross multiplication
M = 60×5.25/1.5
= 315/1.5
= 210 g/mol
Thus molecular mass of the substance is 210g/mol.
Hence,
(a) 210.0 g mol^-1 is the correct answer.