Q. At certain temperature a 5.12% solution of cane sugar is isotonic with a 0.9% solution of an unknown solute. The molar mass of solute is
A) 60
B) 46.17
C) 120
D) 90
Explanation
(a)
“Solutions having same osmotic pressure are called isotonic solutions.” The osmotic pressure is given as
$\therefore$ $\ \ \ \ \ \pi = \frac{w_{b}RT}{VM_{B}}\ \ \ \ \ \ \ \ \ \$
$\ \pi$ (cane sugar)=$\pi$ (unknown solute)
$\frac{5.12}{342} = \frac{0.9}{M}$
M=$\frac{342 \times 0.9}{5.12}$
=60
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.