The solution formed a precipitate when HBr is added. This indicates that the cation present would be silver ion(Ag[tex]^{+}[/tex]) as silver forms an insoluble precipitate with bromide ion.
The equation representing the formation of silver bromide precipitate is:
[tex]Ag^{+}(aq)+HBr(aq)-->AgBr(s)+H^{+}(aq)[/tex]
Bromides of all the other cations,[tex]Cu^{2+},Ag^{+},Ba^{2+},Mn^{2+}[/tex]are soluble in aqueous solutions.
After removing the precipitate of AgBr by filtration, the supernatant solution is treated with [tex]H_{2}SO_{4}[/tex]and another precipitate forms. This would be due to the presence of [tex]Ba^{2+}[/tex]ions as barium sulfate is an insoluble precipitate.
The equation representing the formation of barium sulfate precipitate is:
[tex]Ba^{2+}(aq)+H_{2}SO_{4}(aq)-->BaSO_{4}(s)+2H^{+}(aq)[/tex]
