Question

What is the osmotic pressure of the solution obtained by mixing $300c{m}^3$ of $2\%$ (mass-volume) solution of urea with $300c{m}^3$ of $3.42\%$ solution of sucrose of ${20}^{o}C$?
($R=0.082Latm{K}^{-1}mo{l}^{-1}$)

• A. 5 atm
• B. 5.2 atm
• C. 2.6 atm
• D. 4.5 atm

Answer 1

Answer: (B)

5.2 atm

$C_1=$Concentration of urea $=\frac{Weight}{molarmass\times totalvolume\left(inL\right)}=\frac{\frac{2}{100}\times 300}{60\times 600\times {10}^{-3}}$

$=\frac{1}{6}$

$C_2=$ Concentration of sucrose $=\frac{\frac{3.42}{100}\times 300}{342\times 600\times {10}^{-3}}=\frac{1}{20}$

$\therefore$ Osmotic pressure $=(C_1+C_2)RT$

$(\frac{1}{6}+\frac{1}{20})\times 0.082\times 293$

$=5.2atm$