Question 6 0.00000 out of 2.00000 points In the winter of 1994 a record low temp

Question

Question 6 0.00000 out of 2.00000 points In the winter of 1994 a record low temperature of-33.9 C was recorded the city of Champaign, Ilinois.In an attempt to prevent ice from freezing on the roads, the city covered the streets with magnesium chloride. The hypothesis was that the salt would melt the ice and dissolve in the water, hopefully lowering the melting point of water enough to prevent the ice from reforming. Calculate the freezing point of a saturated solution of magnesium chloride (MgCl2) in "c given: The maximum amount of magnesium chloride that will dissolve in cold water is 543 g per 100.0 g of water. The molal freezing point depression constant for water is 1.86 "C/m. Selected Answer: [None Given)

Explanation / Answer

Mass og MgCl2 = 54.3 g.

Molar mass of MgCl2 = 24 + 2 ( 35.5 ) = 95g/mol

Moles of MgCl2 = mass / molar mass = 54.3 / 95.0 = 0.572 mol

Mass of solvent = 100.0 g. = 0.1000 kg.

Molality = moles of solute / mass of solvent in kg = 0.572 / 0.1000 = 5.72 m

Kf = 1.86 0C/m

Depreesion in freezing point = Kf * m

0.000 - Tf = 1.86 5.72

Tf = Freezing point of solution = - 1.06 0C

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