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Lv 4
? asked in Science & MathematicsChemistry · 1 decade ago

freezing point of a solution?

What is the freezing point (in degrees C) of each of the solutions below? For water, K = 1.86. The vapor pressure of water at 45.0 degrees C is 71.93 mm Hg. A solution of 10.0 g of in 166 g of water at 45.0 degrees C, assuming complete dissociation. And can you show me how you got to the answer? Thank you.

Update:

The solution is 10 g LiCl in 166 g water.

1 Answer

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  • Bobby
    Lv 7
    1 decade ago
    Favorite Answer

    ΔTf = Kf · mB x i

    ΔTf, the freezing point depression, is defined as Tf (pure solvent) − Tf (solution) = ?

    Kf, the cryoscopic constant = 1.86 for water

    mB is the molality of the solution : 10 g of LiCl = 10 / 42.3944 = 0.236 moles in 166g of H2O

    moles in 1000g = .236 x 1000 / 166 = 1.422m

    i = vant hoff factor = 2 for LiCl ( 2 particles in solution)

    ΔTf =1.86 x 1.422 x 2

    = 5.29

    freezing point is - 5.29 degrees C

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