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 step-by-step. 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