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A `5.25%` solution of a substance is isotonic with a `1.5%` solution of urea (molar mass `= 60g 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. `105.0g "mol"^(-1)`B. `210.0g "mol"^(-1)`C. `90.0g "mol"^(-1)`D. `15.0g "mol"^(-1)` |
Answer» Correct Answer - B Isotonic solution have same osmotic pressure. `pi_(1)=C_(1)RT,pi_(2)=C_(2)RT` For isotonic solution, `pi_(1)=pi_(2)` `therefore C_(1)=C_(2)`. or `(1.5//60)/(V)=(5.25//M)/(V)` [where `M=` molecular weight of the substance] or `(1.5)/(60)=(5.25)/(M)=210`. |
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