Comments on: O Level Chemistry – Qualitative Analysis

By: vee

vee — Sat, 29 Oct 2011 12:07:34 +0000

can you please put the table of qualitative analysis for all metals,nonmetals,gases,solutions.

By: Tamara

Tamara — Mon, 23 May 2011 16:37:49 +0000

Hi, What grade students do O level chemistry?

By: Ella

Ella — Thu, 17 Feb 2011 03:39:22 +0000

Hi. I am an NCEA lvl 2 chemistry student, and we are doing qualitative analisis at the moment. We have been asked to write out the ionic and complex equations that occur while finding the anion and cation PbNO3, in our chart there is no need to write any equations for NO3 as no precipitate is ever formed. However, one of the equations we must write for Pb2+ has stumped me, and I would be very glad if you could help.

I have done the first – add 2 drops of dilute NaOH solution. The resulting ionic equation was Pb2+ + OH- ^ Pb(OH)2.
Then – add excess NaOH solution, precipitate disappears. Pb2+ + 4OH- ^ (Pb(OH)4)2-.

But here is the issue. New sample, add two drops, then excess, NH3 solution. White precipitate forms. I need to write this equation, but how do you write –

Pb2+ + NH3 ^??????????
There is a precipitate so it needs to be an ionic equation. But NH3 has no chrge, it is impossible!

By: zachary

zachary — Mon, 07 Feb 2011 16:42:12 +0000

i got all correct except R. where did the zinc come from??

By: I dont understand

I dont understand — Mon, 15 Nov 2010 17:19:54 +0000

I don’t understand why is Q Ca(OH)2 because i thought it is an alkali and alkali are always soluble in water. So why is a precipitate then?

Definition of precipitate : An insoluble solid in a solution that is produced by a chemical reaction.