[vumpler]

Hello everyone,

I'm new here and plan to hopefully hang out and help when I can, but I have a question to start off.

Today we had our lab final and we won't hear our results back for over a week and I can't stand to wait any longer.  I know I probably failed it, but I still want to know what it would have been  So here is the link to the actual printout we took to lab.
It is in PDF format
 It was a qual lab and I'll give you my results from what I can remember off the top of my head...

Ok when you open that you'll see the writeup and then you'll see the solubility portion.  All 4 of these appeared to be soluble, but he informed me that these tests should be taken with a grain of salt and not carved in stone.  So i used them as a reference at the end.  

I tested my unknown on blue and red litmus paper and there was no change.


Under the category of Functional Group tests: I only had 3 positives:
The Test for unsaturation-reaction with Br₂ was a positive.  
The Test for Organic Acids was a positive.
The Test for Aldehydes and Ketones was a positive.

The rest were negative.  Therefore yeilding it was not an Aldehyde.  

The boiling point was right on 141^degC.  

I suspect it was Propanoic Acid, yet I have no idea.  everything else seems to conflict.  When I had the precipitate form in the aldehyde ketone test I was supposted to take a melting point on it, but I did not due to running out of time so I had to guess when I turned in my results.  I went with Propanoic Acid.  The problem is since I had the precipitate form (the solution did not turn clear by the way) doesn't that mean that the only derivative that it could be is a dinitrophnylhydrazone?

Thanks.

[GCT]

I tested my unknown on blue and red litmus paper and there was no change.

this is somewhat surprising. You tested postive for an organic acid.

also how can it be propanoic acid when you had a postive bromine test?

you'll want to consider which tests are more reliable then others.  Impurities can significantly affect boiling point, particularly if you did not allow the supposedly purified compound to dry for a great period of time.  In most cases, you will have boiling point elevation, so you'll want to consider a lower boiling point value then the one you obtained.  

[vumpler]

this is somewhat surprising. You tested postive for an organic acid.

also how can it be propanoic acid when you had a postive bromine test?

you'll want to consider which tests are more reliable then others.  Impurities can significantly affect boiling point, particularly if you did not allow the supposedly purified compound to dry for a great period of time.  In most cases, you will have boiling point elevation, so you'll want to consider a lower boiling point value then the one you obtained.  

Well it turned out to be propanoic acid.  I got lucky.  My professor said the reason it didnt change the litmus paper is because the litmus paper only shows acids around a ph of 1 and bases around a ph of 14.  If i remember right propoanoic acid was at like 3.2.