Question

How much ethyl alcohol must be added to 1 l of water, so that the solution will freeze at 14f (kf for water = 18.6 k molality1)?

Answer 1

ÀÑswêr:

(14–32) C _________ = _____

9 5

C = 5×(–18)

________

9

= –10°C

ΔTF = KF×1000×Wb

___________

Wb×Mb

Wb = Mass of solute

Mb = molar mass of solute

Wa = mass of solvent

10 = 1.86×1000×Wb

_____________

1000×46

⏩Wb = 247.31 g⏪