Qualification > Sciences
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:
--- Quote from: |\/|.A.|\|.B.|.R. on October 26, 2009, 06:16:39 am ---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 .
--- End quote ---
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:
--- Quote from: @d!_†oX!© on October 26, 2009, 04:51:09 am ---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 "
--- End quote ---
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????
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