Homework Help: chemistry... please help!

Posted by Anonymous on Friday, February 13, 2009 at 1:54pm.

Pure glacial acetic acid HC2H3O2 has a freezing point of 16.62 degrees C. Its freezing point depression constant is Kf=3.57 Cm^-1. A solution was made by taking 9.755 g of an unknown non-electrolyte and dissolving it in 90.50 g of glacial acetic acid. The measured freezing point of the solution was 8.64 degrees C. Find the molecular weight of the unknown substance.

chemistry... please help! - bobpursley, Friday, February 13, 2009 at 2:55pm
depression=molality*Kf
= gramsunknown*Kf/(molmassunk*.0905)

solve for molmassunk.

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