Pure Glacial Acetic Acid, HC₂H₃O₂, Has a Freezing Point of 16.62°C

Multiple Choice

Pure glacial acetic acid, HC₂H₃O₂, has a freezing point of 16.62°C. Its freezing point depression constant is: K_f = 3.57 °C m^-1. A solution was made by taking 9.755 g of an unknown nonelectrolyte and dissolving it in 90.50 g of glacial acetic acid. The measured freezing point of the solution was 8.64°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A) 24.4 g mol^-1
B) 30.5 g mol^-1
C) 45.3 g mol^-1
D) 48.2 g mol^-1
E) 174 g mol^-1