Asked by Cerra
In an experiment, 3.545 grams of an unknown nonelectrolyte is dissolved in 15.0 grams of water. The extrapolated freezing point is -.56 degrees C. What is the molecular weight of the unknown material?
Answers
Answered by
DrBob222
delta T = Kf*molality
Solve for molality.
m = moles/kg solvent
Solve for moles. You have m and 0.15 kg solvent)
moles = grams/molar mass
You have moles and grams, solve for molar mass.
Solve for molality.
m = moles/kg solvent
Solve for moles. You have m and 0.15 kg solvent)
moles = grams/molar mass
You have moles and grams, solve for molar mass.
Answered by
Cerra
Ok so when I solved for molality I got 0.30108. Then I plugged in and solved for moles and I got .0045 moles. So when I solved for molar mass I got 784.96 g/mol. Does that sound right? Thank you so much!!
Answered by
DrBob222
That looks ok to me. I think you are allowed only three significant figures so I would round to 785.
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