Precipitation Reactions (1 Viewer)

[jumb]

What do we need to know?

AND

How do you remeber them?

 

[sub]

just try to kno ur solubility rules...all group one elements are soluble, all ammonia and nitrates are soluble, lead precipitates out chlorine.

if u need more consult conq chem...its got a table that u should know for the identification of cations and anions.
also more reactive metals displace less reactive metals...the same is true for anions. that way u can get displacement reactions too.
im not sure if this was what u wer looking for tho.

 

[Xayma]

You need to be able to describe the experiment you did to show trace elements, which pretty much is your solubility rules.

You also need to know flame test.

 

[jumb]

Dont we also need to know the colour of each precipitation though?

 

[sub]

more often than not they're white...lead + iodine gives yellow precipitate...i suggest using that if they ask, how would u kno if there was lead or silver in a solution. if in doubt...i suggest (in an exam situation) think white. cos more often than not that's what they r.
goodluck tomoro

 

[Paroissien]

Meh. It's not hard to remember

 

[Tommy_Lamp]

It's a flow chart, I've written one up and I think its on the resources page.

 

[lucyinthehole]

Meh. It's not hard to remember

well, good for you that you find it easy, but obvioulsly some of us don't

 

[Paroissien]

I only said that in reference to the colour of precipitates, and the range isn't too great

 

[jumb]

I only said that in reference to the colour of precipitates, and the range isn't too great

Brown, Blues, White, Creams, Yellows and reds from what I remember.

 

[sub]

jumb which ones exactly...im pretty sure u dun need to remember all of them, only the ones listed in monitoring part of the syllabus. with cation/anion detection.

 

[Xayma]

more often than not they're white...lead + iodine gives yellow precipitate...i suggest using that if they ask, how would u kno if there was lead or silver in a solution. if in doubt...i suggest (in an exam situation) think white. cos more often than not that's what they r.
goodluck tomoro

Silver and lead you can counter for by adding chloride, heating redissolving lead chloride filtering then adding iodide.

Just remember the order and you will do fine.

 

[jumb]

I hope so.

 

[DAAVE]

Cation Tests:

Add HCl ---> PPT = Pb(2+)

Add H2SO4 ---> PPT = Ca(2+) or Ba(2+)
THEN:
Add F(-) ---> PPT = Ca(2+), No PPT = Ba(2+)

Add NaOH ---> Blue PPT = Cu(2+)
Brown PPT = Fe(3+)
White to Brown PPT = Fe(2+)

Anion Tests

Add HNO3, bubbles = CO3(2-)

Acidify sample, add Ba(2+), PPT = SO4(2-)

Acidify sample, add Ag(+), PPT = Cl(-)

Add NH3 till ph > 9, then add Ba(2+), PPT = PO4(3-)

And add Fe 2+, then H2SO4. If a brown ring forms then its nitrate NO3(-) ions in solution.

U can do that in order if u filter out the ppts and determine if multiple ions are present