Chemistry Practical

[holychalice]

I found it somewhere :
Pb2+ (lead): Original Solution + dil HCl = white ppt, addition of water, boil :
Potassium iodide test: Solution + KI = yellow ppt


Thus , we got a yellow ppt indicating lead .

[Ghost Of Highbury]

I found it somewhere :
Pb2+ (lead): Original Solution + dil HCl = white ppt, addition of water, boil :
Potassium iodide test: Solution + KI = yellow ppt


Thus , we got a yellow ppt indicating lead .

yellow ppt...is already understood..y is lead there?

[holychalice]

Above was the test for lead .....
c we acidified it with nitric acid ... then d residue was taken .. water added to make a solution
Then the KI test was performed ...

[eightAs]

If we are given this test in the qualitative analysis for salts :
" Place the funnel in a test-tube.
Pour about 3 cm3 of dilute nitric
acid onto the residue contained
in the funnel. Add about 2 cm3 of
potassium iodide to the solution
collected in the tube. "

How does it show that the salt is lead carbonate???
even the mark scheme only says : " fizz / bubbles / effervescence "

The fact that the anion is Carbonate is established by the fact that there is effervescence on the addition of a dilute acid. You get that here:
(c) Using a spatula, place a little of C in a test-tube. Add about 2 cm3 of dilute nitric acid and test the gas.
and (d) Place the funnel in a test-tube. Pour about 3 cm3 of dilute nitric acid onto the residue contained in the funnel. Add about 2 cm3 of potassium iodide to the solution collected in the tube.
In both these cases there is effervescence when you added a dilute acid and when tested in (c) the gas was Carbon dioxide so it is definitely a carbonate. There is a yellow ppt formed in (d) possibly because of double displacement. Hence, the insoluble salt must be yellow. We know that Lead Iodide is yellow and insoluble. This fact is used to est for Iodide usually. But in this case it is a test for Lead.

[@d!_†oX!©]

so the whole thing as a whole is the test for lead?
as in a yellow ppt finally shows lead?

[eightAs]

so the whole thing as a whole is the test for lead?
as in a yellow ppt finally shows lead?

Yeah Usually it is used to test for Iodide, but in this case this was ingeniously used to test for Lead.

[@d!_†oX!©]

OK!!!!!!!!!!!!
so d yellow colour actually shows d presence of lead!!!!!!!
ohh
dts cool...didn't know dat!!!
so this provees that the salt is lead carbonate!!!!
By the way eightAs have u seen a test for lead anywhere else except here???it isn't there in the qualitative analysis notes as well!!

[eightAs]

OK!!!!!!!!!!!!
so d yellow colour actually shows d presence of lead!!!!!!!
ohh
dts cool...didn't know dat!!!
so this provees that the salt is lead carbonate!!!!
By the way eightAs have u seen a test for lead anywhere else except here???it isn't there in the qualitative analysis notes as well!!

No it isn't there. During the pre-boards, when we had to do this thingee. I was thinking of the significance of (d). Then I picked up the notes page, looked at all the cations first, no luck. When went to the anion section, I saw the test for Iodide. The yellow ppt thing clicked and I realized it was lead. Tough, I didnt do well in it either cos the chemicals in our school were *******. I couldnt even see limewter going milky, there was just a faint precipitate.

[~~~~shreyapril~~~~]

yupp mann even i read many books ab tests
i did not find in them..
they had only aluminum, copper, ammonia, calcium, iron2, iron3 and zinc i guess
but i feel eightAs' logic is correct

[@d!_†oX!©]

yaa it is correct!! 
thanks alot everyone!!

[~~~~shreyapril~~~~]

By the way this was p6 question riet???
i feel i had seen the same kind somewhere??

[@d!_†oX!©]

naaa
it's paper 5
read on the first page of d thread
may/june 2007

[~~~~shreyapril~~~~]

ohh
so yoou appearing for practicles??
or p6 only??

[@d!_†oX!©]

m doing paper 5 dude

[~~~~shreyapril~~~~]

great mann
do ur best for tmr!!
p5 is practicles... rite???
if not then wat is it??