Solutions Question 3
Question 3 - 25 January - Shift 1
The osmotic pressure of solutions of PVC in cyclohexanone at $300 K$ are plotted on the graph.
The molar mass of PVC is_________ $g mol^{-1}$
(Nearest integer)
(Given : $R=0.083 L atm K^{-1} mol^{-1}$ )
Show Answer
Answer: (41500)
Solution:
$\pi=M^{\prime} RT=(\frac{W / M}{V}) RT$
$\Rightarrow math \pi=(\frac{W}{V})(\frac{1}{M}) RT=C(\frac{RT}{M})$
$\Rightarrow \quad \frac{\pi}{C}=\frac{RT}{M} \neq f(c)$
If we assume graph between $\frac{\pi}{C}$ and $C$
Assuming $\pi$ vs C graph
$ \text{ Slope }=\frac{RT}{M}=\frac{0.083 \times 300}{M \text{ }}=6 \times 10^{-4} $
$\therefore M=\frac{0.083 \times 300}{6 \times 10^{-4}}=\frac{830 \times 300}{6}$
$=41,500 gm / mole$
