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Chemistry coursework, identifying unknown chemicals

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alias25
#1
Dec29-05, 11:55 AM
P: 194
i have to do the plan of my chemistry coursework by monday....

im having trouble with where to start..i have to identify 6 unknown chemicals. im given a list with 8 chemicals that contains the name of 6 unknowns that i have and 2 extras.

im thinking of starting with a litmus paper test for alkaline/acidic. for all the chemicals and grouping them.
(we have limited reagents/test techniques we can use..
we have NaOH, H2SO4, NaHCO3, iodoform test, 2,4-dinitrophenylhydrazine, tollen's reagent. and water of course and bunsen burner)

any help would be appriciated thank you.
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alias25
#2
Dec29-05, 12:05 PM
P: 194
im thinking i could do an iodoform test on them all firslty instead of acid/alkali to test for a CH3 group next to C=O group, is that a good move? bad?
because i, not sure where to go from saying these bunch of chemicals are acidic, i could then do an iodoform test on them...but thats silly if the other bunch of chemical, the alkaline ones have compounds with C=O next to CH3 as well, then i could do iodoform on them too.
i have to reduce the number of test i apply to these chemicals, so i can't just preform all tests on all chemicals.
dfx
#3
Dec29-05, 12:08 PM
P: 60
I don't know about the PH test but I've done the general ID procedure several times - forgotten what it's called actually. My best advice would be to draw up a flow chart that runs over 2 odd pages.

I'll start you off: begin by adding 2-DNPH (to all of them until you get a positive) and that gives you either a POSITIVE or a NEGATIVE (as with any test). If its a POSITIVE you've got your carbonyl compounds, then continue your flow chart to differentiate between the carbonyl compounds. From the NEGATIVE route, go on to test for other compounds using their various tests.

Summing up:

1. Add 2-DNPH
If Positive -> Continue flow chart to differentiate between carbonyls
If Negative -> Begin other tests.

alias25
#4
Dec29-05, 12:16 PM
P: 194
Chemistry coursework, identifying unknown chemicals

but my chemistry teacher advised to start with ph tests...but ill think about it, would you know if sodium hydrogen carbonate would react with anything other than carboxylic acid form that list?

1)can some one tell me the ph of nitriles in particular benzonitrile?

2)0and ethanamide? please i can't find anything by googling.


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