The plot of osmotic pressure ($\Pi$) vs concentration (mol L$^{-1}$) for a solution gives a straight line with slope 25.73 L bar $mol^{-1}$. The temperature at which the osmotic pressure measurement is done is: (Use $R = 0.083$ L bar $mol^{-1} K^{-1}$)

A $25.73^\circ C$

B $12.05^\circ C$

C $37^\circ C$

D $310^\circ C$

The answer is C.

Solution

$\Pi = CRT$; comparing with $y = mx$, the slope m = RT $T = \frac{slope}{R} = \frac{25.73}{0.083} = 310$ K $= (310 - 273)^\circ C = 37^\circ C$

Concept Determining temperature from slope of osmotic pressure vs concentration graph

62 questions from this chapter have appeared across 25 exam years.