Posted by Anonymous on Friday, October 11, 2013 at 3:33am.
A solution contains 10.05 grams of an unknown covalent substance in 50.0
grams of water. The freezing point of this solution is () 3.16o C.
What is the formula weight of the unknown compound?
Below is what I tried, but don't know what to do next. Please explain stepbystep. Thanks
m=3.16/1.86=1.69 moles of solute/kg of water. 10.05 x 1000*50 g/kg of water is 200.4 g. So in l liter we have 1.69 moles = 200.4g. Mass of 1 mole =200.4/1.69 = 118.59

chemistry  DrBob222, Friday, October 11, 2013 at 4:12pm
I don't follow all of you steps but you have essentially the right answer.
10.05 x 1000*50g/kg is not 200.4 and and kg is 50/1000 and not 50*1000. Anyway, here is the way to do it right.
dT = Kf*m
3.16/1.86 = m = 1.6989 (you threw the last 89 away and you should have rounded up to 1.70).
Tnen m = mols/kg solvent or
m x kg solvent = mols = 1.70 x 0.05 kg = 0.0849 mols.
Then mols = grams/molar mass or
molar mass = grams/mols = 10.05/0.0849 = 118.4.
Answer This Question
Related Questions
 CHEMISTRY  A solution contains 10.05 grams of an unknown covalent substance in ...
 Chem9  An aqueous solution containing 35.1 grams of an unknown molecular (...
 Chemistry  Assume that a reaction occurs in which unknown substances R and S ...
 AP Chemistry  An unknown compound contains only the three elements C,H, and O. ...
 Chemistry  Freezing point of pure water = 2, Freezing point of Unknown ...
 college Chemistry  1. If 25 grams of Iron (III) hydroxide is dissolved in a ...
 Chemistry  In an experiment, 3.545 grams of an unknown nonelectrolyte is ...
 Chemistry  Determine the molar mass of a compound and its molecular formula if ...
 Chemistry  An unknown compound contains only carbon, hydrogen, and oxygen. ...
 chemistry  when 10.0 grams of an unknown substance is dissolved in 50. grams of...
More Related Questions