From Dr. Bob's hints, you have
Δ T = i*Kf*M
where M is the number of moles
ΔT = 1.86 °C
i=1
Kf=1.86 °C/m for non-ionizing solutes (check value from your book)
M=ΔT/(i*Kf) mole
Equate this to the mass of solute per 1000 ml. of solution, which we have to assume that the volume of solution equals the volume of water initially to get
M m/l= 62.07/0.5 g/l.
So molar mass
= (62.07/0.5)/M
A solution was made by dissolving 62.07 grams of a compound in 500.0 g of water. The compound was not ionic. The freezing point of the solution was measured and found to be – 1.86oC. Using the Kf value in your textbook , the molar mass of this compound can be calculated to be
a) 57.7 g/mol
b) 124 g/mol
c) 231 g/mol
d) 62.1 g/mol
e) 115 g/mol
bet its e
chemistry - DrBob222, Friday, February 3, 2012 at 6:34pm
If you were betting you lost.
delta T = i*Kf*m
You know dT, i = 1, and Kf. Solve for molality.
Molality = moles/kg solvent.
You have m and kg solvent, solve for moles.
moles solute = n = grams solute/molar mass solute.
You know moles and grams, solve for molar mass.
still lost :(
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