[ecestudent]

For this lab I was given an unknown salt and I so far I have done precipitation tests, found the pH, and found out it decomposes with heat when I did a waters of hydration lab and after about 8 min my unknown was gone.

So far I have:

Flame test seemed like the cation was sodium but I am going to re-do this again tomorrow, it didnt seem to be "enough" orange flame, I then used colbalt glass and didnt see anything. But I want to double check.

pH= 6.02 so it must be a neutral salt

UK+ NaOH= no precipitate
UK+ Na3PO4= no precipitate
UK+ Na2CO3= No precipitate
so it must be a first row cation
   *and when I added a few drops of HCl to the unknown gas was evolved as it seemed, but there were no bubbles. it was just a small amount of white looking smoke. I am not sure what to make of it.
 
then:

UK+ AgNO3= milky white precipitate
UK+ Pb(NO3)2= white precipitate

so far I think the cation is Na+, which is why I want to make sure with another flame test because all the first rows have great color, but the range of anions is still wide.

I am not sure what to conclude or what other tests to do, anyone have any suggestions on possible cations/anions and tests I should do? any help is appreciated!

[Borek]

UK+ AgNO3= milky white precipitate
UK+ Pb(NO3)2= white precipitate

the range of anions is still wide.

Really?

[ecestudent]

Cl-, I-, Br-, or a sulfate, maybe a fluoride. ok so maybe not soo many. but I'd rather narrow it down more. I still dont even have my cation all the way down yet. just only that it is a first row

[UG]

If you think it is a sulfate, try adding BaCl₂ to it and see if there is a precipitate.
Just my own two cents, it's probably either a chloride or a bromide. Try adding dilute ammonia to the precipitate you got from adding AgNO₃, if it is AgCl, it will dissolve.

[ecestudent]

I thought about using BaCl₂ but I couldnt find any in the stock room. Im going to look again but thanks for the second suggestion, Im going to try that

[Borek]

Cl-, I-, Br-

Both precipitates were white?

[ecestudent]

yup, what are you getting at?

[UG]

Lead iodide is yellow.

[ecestudent]

ok so I^- is out, thanks

[skyjumper]

Lead bromide melts at about 367 to form a clear liquid, while lead chloride melts at +500 degrees, try a melting point test on the lead precip

[Borek]

Lead bromide melts at about 367 to form a clear liquid, while lead chloride melts at +500 degrees, try a melting point test on the lead precip

Checking if the precipitate dissolves in a hot solution is much easier.

[NaOH]

Maybe its ammonium chloride, on class I made a reaction of ammonium chloride solution and silver nitrate solution and it gave a white percipitate.