Question

When 6.13 g of a certain molecular compound X are dissolved in 90. g of formamide (NH2COH), the freezing point of the solution is measured to be 2.1 °C. Calculate the molar mass of X. If you need any additional information on formamide, use only what you find in the ALEKS Data resource. Also, be sure your answer has a unit symbol, and is rounded to the correct number of significant digits.

Answer 1

321.6 g/Mol

Step-by-step explanation:

mass of solvent in kilograms = 90g/1000 = 0.09 Kg

Given that;

ΔTf = Kf . m . i

Where;

Kf = freezing point constant = 4.25 °C/Kg mol

m = molality of the solution

i = Van't Hoff factor = 1 (since the substance is molecular)

ΔTf = freezing point of pure solvent - freezing point of solution

freezing point of pure solvent = 3 °C

ΔTf = 3 °C - 2.1 °C

ΔTf = 0.9 °C

0.9= 4.25 * 6.13/M/0.09 * 1

0.9= 26.0525/M * 1/0.09

0.9 = 26.0525/0.09 M

0.9 * 0.09M = 26.0525

M = 26.0525/0.9 * 0.09

M= 321.6 g/Mol