My question concerns freezing point depression and boiling point elevation.

Question

Determine the molar concentration of a glycerol and water solution for boiling points of 101.75 degrees C, 100.99 degrees C, and 103.17 degrees C.  

Answer 1

Not sure if you meant to ask for the molar or molal concentration. We will solve for molal concentration since there is not enough information provided to determine molar concentration. Here is the solution for a boiling point of 101.75. You can do the others in an identical fashion, since the only difference will be in the value of ∆T.

∆T = imK

∆T = change in boiling point = 101.75ºC - 100ºC = 1.75º

i = van't Hoff factor for glycerol = 1 (non electrolyte)

m = molal concentration = moles glycerol / kg water = ?

K = boiling constant for water = 0.512º/m

Solving for m, we have...

1.75 = (1)(m)(0.512)

m = 1.75 / (1)(0.512)

m = 3.42 molal