Calculate the osmotic pressure at `0^@C` of a 0.18 m aqueous solution of KCl which freezes at `-0.68^@C`. Assume volume of solution to be that of pure `H_2O`.
`(K_f " for water " = 1.86^@Cm^(-1))`

Options

A. 4 atm
B. 8.1 atm
C. 3 atm
D. 0.81 atm

Answer

B

Explanation

`DeltaT_f=K_f xx m = 1.86 xx 0.18 = 0.34`
`l = ("Observed" DeltaT_f)/("Calculated" DeltaT_f) = (0.68)/(0.34)=2`
`pi= i CRT= 2 xx 0.18 xx 0.0821 xx 273 = 8.1` atm
Volume of solution = volume of solvent `(H_2O)` and density of `H_2O = 1g//mL`