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 â15.0Â°c? (for water, kf = 1.86 Â°c/m.) ?

Question

Chemistry

Ann Lawson

7 August, 07:29

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 â15.0Â°c? (for water, kf = 1.86 Â°c/m.) ?

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Nayeli Villanueva · Answer 1

According to this formula:

ΔTf = i Kf m

i is van't Hoff factor = 1

Kf = 1.86

m the molality we need to assume it

m = x moles of C2H5OH / Kg of mass

∴ 15 = 1 * 1.86 * (x moles of C2H5OH / 0.45 kg)

∴X = 3.629 moles

mass = no. of moles x molar mass of C2H5OH

= 3.629 X 46 = 167 g

∴the volume = mass / denisty

= 167 / 0.7893 = 211.57≈ 212 mL