[methlover]

In lab, I'm doing a qualitative analysis of a simple salt to figure out what the salt is.  My unknown salt(which is white) could be a combination of any of these:

Cations: Ag+, Pb2+, Bi3+, Sb3+, Sb5+, Sn2+, Sn4+, Al3+, Zn2+
Anions: NO3-, Cl-, Br-, I-, (SO4)2-

Possibilities of cations and anions were actually more than the listed, but after testing solubilities of the salt in water.  I narrowed down some of cations and anions.

The salt was VERY soluble in water, soluble in HCl, slightly soluble in HNO3, mostly soluble in NaOH, and insoluble in 3M of NH3.  All the solutions were colorless or a bit foggy in some(if I remember this correctly), and if there were precipitates, color of the solid didn't change.

I've done some research and reading for all the possible combinations, and this is what I have so far.

If the cation is Ag+, it could only be AgNO3
If the cation is Pb2+, it could only be Pb(NO3)2.
If the cation is Bi3+, it could be Bi(NO3)3, BiCl3, or Bi2(SO4)3
If the cation is Al3+, it could be Al(NO3)3, AlCl3, AlBr3, AlI3, or Al(SO4)3.. so hopefully it's not Aluminum(III)..
If the cation is Zinc, and again, it could be all the possible combinations just like Aluminum.

But from what I've researched, ZnCl2 and ZnI2 are VERY soluble in H2O.  So I'm thinking the possibilities of salt being ZnCL2 and ZnI2 are greater than any others.

what should I test out for?
And if my cation happens to be antimony or tin, how would i test out if the charge is 3+/5+ or 2+/4+
Any tips or suggestions would be great!

[methlover]

And for determining cation, how should I check out which cation I have?
Should I just test out by adding different ions' confirming reagent and observe?

[AWK]

Zinc salts are very soluble in ammonia!

[methlover]

thanks. a very good tip since zinc confirming test is probably the longest in time wise.  I've somehow narrowed down my choices.  I figured it wouldn't be Ag+ or Pb2+ since the unknown solid was soluble in HCl.(Ag or Pb2+ should precipitate when they are dissolved in HCl.)  So that narrows down my cations to Bi3+, Antimony, Tin and aluminum.

Just to make sure, so any sorts of zinc salts are very soluble in ammonia?(3M, 6M, etc)

More tips are appreciated

[AWK]

Ammonia precipitates hydroxides of Bi and Al

[methlover]

good information. i will test out Bi or Al first.  Hopefully it's one of the two.
If not, I will have to test out Antimony/Tin

[methlover]

thanks for your useful tips!
I tested out for aluminum first, and my cation was aluminum!!!!

Now all I've got to to do is find out what my anion is.
I am going to test out for halides first then nitrate.

Any suggestions?

[AWK]

You wrote:

and insoluble in 3M of NH3

this cannot be  Al³⁺
if your information was correct

[methlover]

Do you mind explaning why it cannot be Al3+

These are possible cations: Ag+, Pb2+, Bi3+, Sb3+, Sb5+, Sn2+, Sn4+, Al3+, Zn2+
I figured it wouldn't be Ag+ or Pb2+ since my unknown salt dissolved completely in HCl.  (If it had been Ag+ or Pb2+, it would have precipitated in HCl solution.)

Now, you've mentioned that Zinc salts are VERY soluble in ammonia, so I crossed that one out.

All I left with were Bi3+, antimony, tin or aluminum.  Follow me, so far?
I tested out for aluminum first(making it to Al(OH)3 by following my lab notebook procedure and mixing with confirming reagent.) Alas, I cannot remember all the steps for confirmation of Al3+, but it requires some heating, centrifuging, etc.

I've done Al3+ confirmation test for another lab a few weeks ago.  When Al3+ is present in a salt and when you pour in a confirming reagent, a filmy red precipitate shows up

So I tested out for Al3+ today, after all the confirmation test in the end, I had a filmy red precipitate on the bottom of the test tube.  Now, that confirms the fact that the unknown salt's cation is Al3+.

[AWK]

Of course, alizarin test is quite specific for Al³⁺, if properly done. But you told us your salt is soluble in ammonia, whereus Al salt form  insoluble Al(OH)3 with ammonia. This was true or false information?

[methlover]

I think you might have misread/misunderstood my first post.
In my very first post, I stated, "The salt was VERY soluble in water, soluble in HCl, slightly soluble in HNO3, mostly soluble in NaOH, and insoluble in 3M of NH3."

So, the salt was insoluble in Ammonia.
I really appreciate your previous tips though.  You really saved most of my time... I wouldn't have found what my cation was without the tips/it would have taken me several days.  Thanks for the big help

Now, all I have to do is find the anion.

[methlover]

Which anion should I test out first?
Halides, Sulfite or nitrate?

[Borek]

Follow standard approach...

Elements Of Qualitative Chemical Analysis - Welday Scott, Wilfred.
http://www.archive.org/details/elementsofqualit029597mbp

Semi Micro Qualitative Analysis - Arthur,Paul.
http://www.archive.org/details/semimicroqualita029128mbp

You don't have to do complete analysis, just follow determination order as described in these books.

[methlover]

those are great sites, but I've already got my cation and narrowed my possibilities of anions: halides, sulfites and nitrates.

I was just asking which anion would more likely to be the anion of my salt so that I can test out right ahead tomorrow and save some time.

[Borek]

First book explains anion analysis starting on page 105 - looks to me like you could just follow the order proposed there.