Q. What is the amount of urea dissolved per litre if its aqueous solution is isotonic with 10% cane sugar solution? (mol.wt.of urea =60)
A) 200 g/L
B) 19.2 g/L
C) 17.54 g/L
D) 16.7 g/L
Explanation
(c)
$\pi V = \frac{W}{m}\ RT$
for isotonic solutions, osmotic pressure ($\pi$) is same
$\frac{W_{1}}{m_{1}V_{1}} = \frac{W_{2}}{m_{2}V_{2}}\ \$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ V_{1} = 1L,\ V_{2} = 100\ mL = 0.1L\$
$\frac{W_{1}}{60 \times 1} = \frac{10}{342 \times 0.1}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ W_{1} = 17.54\frac{g}{L}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.