Chem21Labs The minor componet in a solution dissolved in the solvent. c. solute

Question

Chem21Labs The minor componet in a solution dissolved in the solvent. c. solute NC Edit Answer 3. C2H,02 is infinitely miscible (soluble) in water. Ethylene glycol is a nonelectrolyte that is used as antifreeze. What is the lowest possible melting point for engine coolant that is 278 % (by mass) ethylene glycol? Kr for H20 is 1.86 C/m NG 4. A 1.6467 g sample of an unknown nonelectrolyte dissolved in 11.4311 g of benzophenone produces a solution that freezes at 31.700. If the pure benzophenone melted at 47.5 C, what is the molecular weight of the unknown compound? NG Kr for Benzophenone is 9.8 °C/m Earned Total Points- 0 View Printable Page 14

Explanation / Answer

3.

Mass of ethylene glycol = 27.8

Molar mass of ethylene glycol = 2 ( 12 ) + 6 ( 1 ) + 2 ( 16) = 62 g/mol

Moles of ethylene glycol = mass / molar mass = 27.8 / 62 = 0.448 mol

Mass of water = 100 - 27.8 = 72.2 g. = 0.0722 kg.

Molality of solution = moles of solute / mass of solvent in kg = 0.448 / 0.0722 = 6.21 m

We know that,

depreesion in freezing point = Kf * molality

T0 - T = 1.86 * 6.21

0 - T = 11.6

T = leat possible melting point = - 11.6 0C

4.

Depression in freezing point = Kf * m

47.5 - 31.7 = 9.8 * m

m = molality = 1.61 m

But,

molality = moles of solute / mass of solvent in kg.

1.61 = moles of solute / 0.0114311

Moles of solute = 0.0184 mol

But ,

Number of moles = mass / molar mass

0.0184 = 1.6467 / molar mass of solute

Molar mass of solute = 89.4 g/mol

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