Question

suppose you have a solution that might contain any or all of the following cations: Cu2+, Ag+,Ba2+ and Mn2+. The addition of HBr causes a precipitate form. after the precipitate is separated by filtration, H2SO4 is added to the supernatant liquid, and another precipitate forms.

Answer 1

The solution formed a precipitate when HBr is added. This indicates that the cation present would be silver ion(Ag
`^(+)`) as silver forms an insoluble precipitate with bromide ion.

The equation representing the formation of silver bromide precipitate is:

`Ag^(+)(aq)+HBr(aq)-->AgBr(s)+H^(+)(aq)`

Bromides of all the other cations,
`Cu^(2+),Ag^(+),Ba^(2+),Mn^(2+)`are soluble in aqueous solutions.

After removing the precipitate of AgBr by filtration, the supernatant solution is treated with
`H_(2)SO_(4)`and another precipitate forms. This would be due to the presence of
`Ba^(2+)`ions as barium sulfate is an insoluble precipitate.

The equation representing the formation of barium sulfate precipitate is:

`Ba^(2+)(aq)+H_(2)SO_(4)(aq)-->BaSO_(4)(s)+2H^(+)(aq)`