Question

When 908.0 mg of a certain molecular compound X are dissolved in 40.0 g of dibenzyl ether ((C₆H₅CH₂)₂0), freezing point of the solution is measured to be -3.2 °C.

Calculate the molar mass of X. If you need any additional information on dibenzyl ether, use only what you find in the ALEKS Data resource. Also, be sure your answer has a unit symbol, a is rounded to the correct number of significant digits.

Answer 1

The molar mass of compound X is 20.9 g/mol

Step-by-step explanation:

Step 1: Data given

Mass of compound X = 908.0 mg = 0.908 grams

Mass of dibenzyl ether = 40.0 grams = 0.040 kg

freezing point of the solution = -3.2 °C.

Freezing point depression constant = 6.27 °C/m

Freezing point of pure dibenzyl ether = 3.6 °C

Step 2: Calculate molality

ΔT = i*Kf*m

⇒with ΔT = the freezing point depression = 6.8°C

⇒with i = the can't Hoff f = 1

⇒with Kf =Freezing point depression constant = 6.27 °C/m

⇒with m = the molality = TO BE DETERMINED

6.8 = 6.27 * m

m = 1.085 molal

Step 3: Calculate moles compound X

Moles compound X = molality * mass dibenzyl ether

Moles compound X = 1.085 molal * 0.040 kg

Moles compound X = 0.0434 moles

Step 4: Calculate molar mass of compound X

Molar mass = mass / moles

Molar mass = 0.908 grams / 0.0434 moles

Molar mass = 20.9 g/mol

The molar mass of compound X is 20.9 g/mol