Question

a 0.15 m aqueous solution of KCl freezes at -0. 510 °C. Calculate i and osmotic pressure at 0°C. Assume volume of solution is equal to that of water. ​

Answer 1

Given:

Molality, m = 0.15 m

ΔTf = 0.510 °C = 0.510 K

T = 0 °C  = 273 K

To Find:

Van't hoff factor and osmotic pressure.

Calculation:

- We know that depression in freezing point is given as:

ΔTf = i × Kf × m

⇒ i = ΔTf / (Kf × m)

⇒ i = 0. 510 / (1.86 × 0.15)

⇒ i = 1.828

- Now, we know that osmotic pressure is given by:

Π = i × C × R × T

⇒ Π = 1.828 × 0.15 × 0.083 × 273

⇒ Π = 6.213 bar

- So, the Van't hoff factor (i) is 1.828 and Osmotic Pressure (Π) is 6.213 bar.