qualitative analysis help...

[hassam]

if for e.g we were given coloured solution like copper chloride which is blue and chromium chloride how cn we test for halide ion....b/c solutions are coloured and it will be smwat difficult to record white ppt

 

[CaptainDanger]

Ummmm... Copper Chloride is light brown in colour not blue... For Chloride ions you have the following test...

TEST
1. Add a little dilute Nitric Acid(TO REMOVE ANY CARBONATE IF PRESENT)

2. Add Silver Nitrate solution.

OBSERVATION

A white precipitate is formed of silver chloride...

The white ppt is clearly seen.... Colours disappear...

 

[farrukh]

you will have to filter the solution and wash the ppt.

 

[CaptainDanger]

Right...

 

[diwash]

why do we need to remove carbonate before checking for any ppt?

 

[CaptainDanger]

As you are testing for chloride ions... So any carbonate ions needs to be removed.... Or any other ions... Which can give confusing precipitate and the test can go wrong....

 

[hassam]

hey..plx tell me abt Al,Pb,Zn.....cations.....also tell if they dissolve in excess wat their soln looks like.......and having difficulty with finding whether its a ppt or has it dissolved...wats standard method for that...thanx

 

[CaptainDanger]

If you test them with sodium hydroxide they dissolve in excess, for all the three you mentioned the solution is colorless.... While if the reagent you use is aqueous Ammonia then only Zn dissolves in excess, Al and Pb remain insoluble... Other then that you can watch some good videos on youtube... It will make it clear to u...

 

[hassam]

and for distinguishing Al FROM Pb we shoud use....sodium chloride ryt....

 

[CaptainDanger]

Sodium Chloride???? How??? :ugeek:

 

[hassam]

lead chloride will precipitate out

 

[hassam]

how i will know that i have to test for a particular gas and not the other ones.......plxxx helpp

 

[CaptainDanger]

Oh alright.... Every gas test has its own end result....???? That will tell you about it...

 

[hassam]

no man....ho i will know to test for a particular gas when i ll be testing with unknown solutions

 

[CaptainDanger]

No idea... Sorry....