Finding The Identity of Unknowns

1. May 17, 2005

don123

For my chem class my teacher is going to give us 2 unknowns and we have to find out their identity. How would you do this?

I figured that you would heat the liquids to figure out their boiling point and then look in the book (she'll let us use the books) to figure out the substaNce.

I could also do the color test lab but I don't think that it is very effective.

BTW I posted this in Chem section and didn't get respons so I figured I'd try here.

2. May 17, 2005

saltydog

Hello Don.
Surely you must have some general guidelines and have at least some idea what it is right? Generally you'll have some qualitative scheme to "narrow down" the possible candidates. Have you been given this? Is is both two liquids? Both organic? Polar, non-polar? Volatile? I don't know about the heating up part. You know, you can just wave your hand over it carefully to get just a tiny and I mean tiny wiff of it. You know basic rule of Chemistry is NOT to put your nose to it right? Well, I don't know what you know. Smells like alcohol, we're on our way.

Edit: I think color test are effective if done in a methodical way and used with other evidence.

Last edited: May 17, 2005
3. May 17, 2005

BobG

Boiling point is one good indicator. The density is another. You can also do solubility tests (is the unknown liquid dissolved and completely mixed with the solvent or do they form layers, etc.). In fact, I imagine that either your text book or lab book has a table that lists all three characteristics (boiling point, density, & a solubility chart). If not, I'm sure the lab has a reference that does (the CRC book is a good reference - even if I can't remember it's full name, I think it normally has a dark red cover :rofl: ).