Question

Dissolution of 1.5g of a non-volatile solute (mol., wt. = 60) in 250 g of a solvent reduces its frezzing point by `0.01^(@)C` . Find the molal depression constant of the solvent.
A. `0.01`
B. `0.001`
C. `0.0001`
D. `0.1`

Answer 1

Correct Answer - D
Depression in frezzing point ,
`Delta T_(f) = k_(f) xx m`
where , m= molality = `("wt. of solute" xx 1000)/("mol. Wt. of solute") xx "wt. of solvent" `
`= (1.5 xx 1000)/(60 xx 250)`
`=0.1`
`implies Delta T_(f) = k_(f) xx 0.1`
`0.01 = k_(f) xx 0.1`
`therefore k_(f) = (0.01)/(0.1)`
`= 0.1 ^(@)C "molal"^(-1)`