Question

The freezing point of benzene solution was ${5.4}^{o}C$. The osmotic pressure of same solution at ${10}^{o}C$ is: (freezing point of benzene $={5.5}^{o}C$). Assume solution to be dilute. $(K_f$ for $C_6{H}_6$ is 4.9 K $molalit{y}^{-1})$

• A. $0.274$ atm
• B. $0.474$ atm
• C. $0.674$ atm
• D. $0.874$ atm

Answer 1

Answer: (B)

$0.474$ atm

The osmotic pressure of same solution is $0.474atm$

$\Delta T_f=5.5-5.4={0.1}^{o}C$

$\pi =C_{M}ST(C+M=molarity)$

$\Delta T_f=C_m\times K_f(C_m=molality)$
for dilute solutions $C_M=C_m$

$\therefore \pi =\frac{\Delta T_f}{K_f}\times ST=\frac{0.1}{4.9}\times 0.0821\times 283=0.474atm$