Question 8 1 pts If we have three different solutions, A, B, and C, each contain

Question

Question 8 1 pts If we have three different solutions, A, B, and C, each containing 100. grams of water, plus respectively 34.2 g of sucrose, 4.6 g of ethanol, and 4.0 g of sodium hydroxide, which statement is true? Molar Masses surcose, C12H22011 342.0 g/mol ethanol, C2HsOH 46.0 g/mol sodium hydroxide, NaOH 40.0 g/mol 0 A, B, and C all have different freezing points. O A, B, and C will all have the same freezing points. ° C has the lowest freezing point in the group. The boiling point of C is lower than that of A or B OA and C have the same boiling point, but B has a lower one

Explanation / Answer

The formula for calculating freezing point depression is

Tm=Kfm

where

Tf is the decrease in freezing point
Kf is the molal freezing point depression constant
m is the molality of the solution.

Molality=moles of solute kilograms of solvent

Let's rewrite this formula in symbols as

m=n/m'

Then

Tf=Kf(n/m') where n=moles of solute and m' = mass of solvent

if the mass of the solvent (water) is same then, then freezing point depends on moles of solute,

moles of sucrose in A = 34.2/342= .1

moles of ethanol in B = 4.6/46= .1

moles of sodium hydroxide in C =4/40 = .1

so moles of solute is same then freezing point depression will be same so, the freezing point of A, B, and C all are same.

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