how do you find an unknown cation??? (1 Viewer)

[4lettersdown]

hey guys, i posted this in chemical monitoring and management, but it wasnt getting a response.



Hey guys, just looking over my stuff for tommorow when I realise I'm not really all that great on identifying unknown Ions. i think ive got the anion one down:
start with PO₄^3-, CO₃^2-, SO₄^2-,Cl^2-.
add AgNo₃
yellow precipitate shows PO₄^3-
white - everything else
Add BaNO₃
No precipitate - Cl^2-
Precipitate - everything else
add an Acid
bubbles-CO₃^2-
no bubbles-SO₄^2-

Do we need it in this much detail, and is that all correct etc, and if so, can someone pelase link me (or tell ma) a cation one?
and I'm also kinda stuck on the flame testing and solubility rules.
thanks in advance (I hope)

 

[mirror-match]

Sorry bro, not meaning to be a dick, but I highly doubt that your gonna get a response this close to the exam. Its pretty much jeopardising a couple marks that you might beat someone with. Unless its someone that's already completed there HSC.

 

[nosh22]

Yes there is a cation one.

If you get a precipitate with HCl -> You have Pb
If you get a precipitate with H2SO4 -> You have Ba or Ca
If you get a precipitate with NaOH -> You have Cu, Fe2+ or Fe3+


I think... From the top of my head.

 

[nosh22]

Sorry bro, not meaning to be a dick, but I highly doubt that your gonna get a response this close to the exam. Its pretty much jeopardising a couple marks that you might beat someone with. Unless its someone that's already completed there HSC.

I'm nice. And also, telling someone else consolidates my learning.

 

[4lettersdown]

thanks alot man, I really didnt expect a response. epic reps.
(actually I can;t because Ive already repped you once but owell, the thought counts)

 

[mR sinister]

Hope this isnt too late

Test for identifying cations

Cation Test
ba^2+ = add CO32-, SO42-, PO43- and white ppt forms
Ca^2+ = add OH-, SO42-, PO43- and white ppt forms
pb^2+ = add CL-,OH-,SO42-,CO32-,PO43- and white ppt forms
Cu^2+ = add OH- and blue ppt forms
fe^2+ = add OH- and white ppt forms which quickly turns brown.

test for identifying Anions

Anioin Test
SO42- = forms white ppt with BaNO3, CaNO3, PbNO3 and AgNO3
PO43- = forms yellow ppt with HNO3
CL- = forms white ppt with AgNO3
CO32- = forms CO2 gas when an acid is added.

Hope that helps, that wat i learnt for them

 

[thisnameistaken]

If it asks for a confirmation test ill just say AAS

 

[annabackwards]

Ah, you need to know this. The easiest way to remember it is in a flowchart form.

Click here to go to the CSU site. Scroll down a bit and you'll see a flowchart.

Memorise it

If it asks for a confirmation test ill just say AAS

You won't get marks for that at all because AAS is a solely quantitative test.

 

[shady145]

and your chlorine ion has the wrong charge... =)

 

[shady145]

Hope this isnt too late

Test for identifying cations

Cation Test
ba^2+ = add CO32-, SO42-, PO43- and white ppt forms
Ca^2+ = add OH-, SO42-, PO43- and white ppt forms
pb^2+ = add CL-,OH-,SO42-,CO32-,PO43- and white ppt forms
Cu^2+ = add OH- and blue ppt forms
fe^2+ = add OH- and white ppt forms which quickly turns brown.

test for identifying Anions

Anioin Test
SO42- = forms white ppt with BaNO3, CaNO3, PbNO3 and AgNO3
PO43- = forms yellow ppt with HNO3
CL- = forms white ppt with AgNO3
CO32- = forms CO2 gas when an acid is added.

Hope that helps, that wat i learnt for them

also flame tests for 3 cations
Ba2+ = yellow-green
Cu2+ = green
Ca2+ = brick red