A 0.10 M aqueous solution of a monoprotic acid `("d=1.01 g/cm"^3)` is 5% ionized. What is the freezing point of the solution? The mol.wt. of the acid is 300 and `K_f (H_(2)O)="1.86"^@C//m:`

Options

A. `-0.189""^(@)C`
B. `-0.194""^(@)C`
C. `-0.199""^(@)C`
D. `-0.173""^(@)C`

Answer

C

Explanation

Mass of 1 litre of solution =1010g, mass of solvent `=1010-300 xx 0.1 rArr 980g`
`m=(0.1)/(0.98) rArr 0.102, Delta T_(f) = K_(f) mi= (1+ alpha) K_(f).m`
`Delta T_(f)= 1.05 xx 1.86 xx 0.102 = 0.199^(@)C, T_(f)= 0-0.199 = - 0.199^(@)C`