Question

The osmotic pressure of the solution obtained by mixing $200{cm}^3$ of $2$%(mass-volume) solution of urea with $200{cm}^3$ of $3.42\%$ solution of sucrose at ${20}^{o}C$ is:

• A. $4bar$
• B. $1.2bar$
• C. $5.2bar$
• D. $2.6bar$

Answer 1

The correct option is D $2.6bar$

$\pi =$ Osmotic pressure $=CRT$ $R=0.082$ Latm/K/mol

$C=$ Molar concentration $T=20+273=293K$

In $400ml$ of solution we have

Solute $=\frac{2}{60}+\frac{3.42}{342}$ Molar mass of urea $=60$

$=0.043$ moles Sucrose $=342$

$=\frac{0.043\times 1000}{400}$

$=0.108M$

$\therefore$ $\pi =0.108\times 0.082\times 293$

$=2.594$ atm

we know that 1 atm =1.01325 bar

So, $\pi =2.594\times 1.01325\approx 2.60bar$

Hence, the correct option is D.