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Lauryl alcohol is obtained from cocon ut oil and is used to make detergents. A solution of 5.00 g of lauryl alcohol in 0.100 kg of benzene freezes at 4.1°C.
a. What is the molar mass of lauryl alcohol from this data?

Respuesta :

Answer:

185.2 g/mol.

Explanation:

Solvent = Benzene

Solute = lauryl alcohol

Given:

Mass of solute = 5 g

Mass of solvent = 0.1 kg

Freezing point of solvent, Temp.f = 4.1 °C

Initial freezing point of solvent, Temp.i = 5.5 °C

Molal freezing depression constant for Benzene, kf = 5.12 °C/m

ΔTemp.f = Temp.f - Temp.i

= 5.5 - 4.1

= 1.4 °C

ΔTemp.f = kf * m

Where m = molality

m = 1.4/5.12

= 0.27 mol/kg

Molality = number of moles of solute/mass of solvent

Number of moles = 0.27/0.1

= 0.027 mol.

Molar mass = mass/number of moles

= 5/0.027

= 185.2 g/mol.

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