[yankae]

Can someone kindly tell me what are the things i need to know for o-level chemical analysis for cation and anion, eg.

colourless solution of white crystal A --HCl-> colourless gas B --limewater-> whiteppt C

By the way, I dont understand why the anion can be "colourless solution of white crystal A"

I have already tried searching my textbk and internet but to no avail...
Tell me please Thanks

[Arkcon]

Try to work it backwards, limewater has one application for analytical chemistry, it identifies one gas, which is produced from one anion when treated with acid.  The final answer, is of course, only half of the answer you'll eventually need, if you are to identify is solid for an O-level exam.