1. Tardigrade
  2. Question
  3. Chemistry
  4. 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 solution are assumed to be equal to 1.0 g cm-3 molar mass of the substance will be

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Q. 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 solution are assumed to be equal to $1.0 \,g \,cm^{-3}$ molar mass of the substance will be

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Solution:

Isotonic solutions have the same molar concentration. Hence,
Molar cone. of the substance=Molar cone of urea
$\frac{52.5 g \, L^{-1}}{M} = \frac{15 \, g \, L^{-1}}{60 g\, mol^{-1}}$
(100 g solution = 100 mL as d = 1 g $mol^{-1}$)
M = $\frac{52.5 \times 60}{15} $ = 210 g mol$^{-1}$