Question

A`5%` solution of cane sugar (molar mass =`342`)is isotonic with `1%`of a solution of an known solute.The molar mass of unknown solute in g/mol is
A. 60
B. `46.17`
C. 120
D. 90

Answer 1

Correct Answer - A
Isotonic solutions are those which have same osmotic pressure, hence have same concentration.
Normality of 5.12% solution of cane sugar `=(5.12xx1000)/(342xx100)`
Normality of 0.9% solution of unknown solute `=(0.9xx1000)/(M xx100)`
`(5.12xx1000)/(342xx100)=(0.9xx1000)/(M xx100)` or, M = 60.1