Question: 84. The plot of osmotic pressure ( \Pi ) vs concentration (mol \mathrm{L}^{-1} ) for a solution gives a straight line with slope 25.73 \mathrm{~L}^{-1} bar \mathrm{mol}^{-1}. The temperature at which the osmotic pressure measurement is done is:
(Use \mathrm{R}=0.083 \mathrm{~L} bar \mathrm{mol}^{-1} \mathrm{~K}^{-1} )
(1) 37^{\circ} \mathrm{C}
(2) 310^{\circ} \mathrm{C}
(3) 25.73^{\circ} \mathrm{C}
(4) 12.05^{\circ} \mathrm{C}
Answer: Option (1)
Explanation:
Osmotic pressure is related to concentration by the equation
\Pi = C R TWhen \Pi is plotted against concentration C,
the slope of the straight line is equal to R T.
Given slope = 25.73 \ \mathrm{L} \ \mathrm{bar} \ \mathrm{mol}^{-1}
Therefore,
R T = 25.73 T = \dfrac{25.73}{0.083} T = 310 \ \mathrm{K}Converting temperature into degree Celsius,
T = 310 - 273 = 37^{\circ}\mathrm{C}Hence, the temperature at which the osmotic pressure measurement is done is
37^{\circ}\mathrm{C}.