Question

Calculate the freezing point and boiling point of aqueous 1.9 m CuCl3 given Kf for water = 1.86 deg.C/m; Kb for water = 0.512 deg C/m. Assume theoretical value for i. Show work for credit.

Answer 1

Freezing point

CuCl3 solution

molality (m) of solution = 1.9 m

Kf = 1.86 oC/m

i = 4 for CuCl3 [1Cu3+ + 3Cl-]

using,

dTf = iKfm

      = 4 x 1.86 x 1.9

      = 14.14 oC

Freezing point of solution = 0 - 14.14 = -14.14 oC

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Boiling point

CuCl3 solution

molality (m) of solution = 1.9 m

Kb = 0.512 oC/m

i = 4 for CuCl3 [1Cu3+ + 3Cl-]

using,

dTb = iKbm

      = 4 x 0.512 x 1.9

      = 3.90 oC

Boiling point of solution = 100 + 3.90 = 103.90 oC