Problem: What volume of ethanol (density = 0.7893 g/cm3) should be added to 450 mL of water in order to have a solution that freezes at -15.0°C? [For water, Kf = 1.86°C/m.]A) 371 mLB) 470 mLC) 212 mLD) 132 mLE) 167 mL 

🤓 Based on our data, we think this question is relevant for Professor Ekanayake's class at KENT.

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FREE Expert Solution

We’re being asked to determine the volume of ethanol (C2H5OH) that must be added to 450 mL water to get a solution with a freezing point of –15.0 ˚C.


Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔT­f) is given by:


ΔTf=Tf, pure solvent-Tf, solution


The change in freezing point is also related to the molality of the solution:


ΔTf=imKf


where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kf = freezing point depression constant (in ˚C/m)


Recall that the molality of a solution is given by:


molality=moles solutekg solvent



For this problem, we need to do the following:

Step 1: Calculate for ΔTf.

Step 2: Determine the molality of the solution.

Step 3: Calculate the volume of C2H5OH needed.


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Problem Details

What volume of ethanol (density = 0.7893 g/cm3) should be added to 450 mL of water in order to have a solution that freezes at -15.0°C? [For water, Kf = 1.86°C/m.]

A) 371 mL

B) 470 mL

C) 212 mL

D) 132 mL

E) 167 mL


 

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Based on our data, we think this problem is relevant for Professor Ekanayake's class at KENT.