Anion Identification (1 Viewer)

[schooly]

Hi all, i was wondering if anyone knows of any nice and simple way/flowchart for the identificaion of anions in mixture. i have seen the www.hsc.csu.edu.au and didnt look like a good one with Fe2+ and Fe3+.
Thankyou

 

[kini mini]

I can't for the life of me remember what the test for Fe2+ and Fe3+ was, I think it was something to do with decolourising a certain solution (Thickett's method) and Roland's has disappeared from my brain...but both Conquering and Pathways have decent flow charts .

 

[mannnnndy]

Heres the one I used:

anion mixture:

- add Fe(3+)
if there is a brown precipitate the anion is OH-

- add Fe(2+)
if there is a green precipitate the anion is PO4(3-)
if there is a grey precipitate the anion is CO3(2-)

- add Ba(2+)
if there is a white precipitate the anion is SO4(2-)

- add Pb(2+)
if there is a white precipitate the anion is Cl-


for the Fe(2+) and Fe(3+) test you add OH- and if there is green precipitate (which later turns brown) then the anion is Fe(2+). If there is a brown precipitate the anion is Fe(3+).

 

[CraZiEeE]

Im not sure if i post this up to late but....i think "mannnnndy" posted up tests referring to cations test...not anions like asked ^^

 

[ND]

Nope they're anions, read them.

edit: woah how old is this thread...

 

[toknblackguy]

hahaha
april
ppl studying back thn?
omgness

 

[mon_mon]

lol. i think my study started about 4 hours ago.

 

[mercury]

1. add KSCN to solution containing Fe 3+, it goes blood red.
Fe 2+ only turns solution red when it gets oxidised to Fe 3+ gradually.

2. And Fe(OH)2 is white but quickly turns to brown as Fe2+ gets oxidised to Fe3+

 

[phenol]

the best test for Fe 2+ and Fe 3+

add KSCN to solution first, if it goes blood re, Fe 3+ present
if nothing happens proceed

add a small amount of acidified potassium dichromate (or maybe you used permanganate in class)
if the solution goes blood red now then Fe 2+ present
if nothing happens then ur solution doesn't have either Fe 2+/Fe 3+ (or maybe just too much base but that shouldn't be the case)

the reason is

dichromate and permanganate are very capable oxidising agents
(around E = - 2.00)

so when u add KSCN nothing happens to Fe 2+ but when u oxidise it to Fe 3+ after adding dichro/permang, it goes completely blood red.