Q. about precipitation (1 Viewer)

[ND]

Why does pH affect precipitation reactions?

edit: quesstion rephrased.

 

[jims]

wat kind of example are you thinking of?

 

[ND]

Well to detect sulfate, you can add HCl (i assume to lower the pH) then add Ba(NO3)2. And to detect phosphate you add NH3 then Ba(NO3)2. Why does the HCl or NH3 have to be added?

 

[shadowRRL]

i didnt know that

 

[Constip8edSkunk]

HCl is to remove carbonates that may precipitate
and
NH3 is to make sure PO4 precipitates not H(or H2)PO4 [edit:]which doesnt precipitate?

 

[ND]

Ah ok, thanks.