2.37 describe tests for the anions: i Cl-, Br- and I-, using dilute nitric acid and silver nitrate solution ii SO4(2-), using dilute hydrochloric acid and barium chloride solution iii CO3(2-), using dilute hydrochloric acid and identifying the carbon dioxide evolved

2.37 •testing for halides with nitric acid and silver nitrate 

        •1. add dilute nitric acid (HNO3) followed by silver nitrate solution (AgNO3)

                  •the acid is added to get rid of carbonate or sulphide ions before the test so that they don't react instead 

        •a chloride ion gives a white precipitate of silver chloride       Ag+(aq) + Cl-(aq) —> AgCl(s)

        •a bromide ion gives a cream precipitate of silver bromide     Ag+(aq) + Br-(Aq) —> AgBr(s)

        •a iodide ion gives a yellow precipitate of silver iodide            Ag+(aq) + I-(aq) —> AgI(s) 

        •silver nitrate + sodium chloride —> silver chloride + sodium nitrate 

                                        •AgNO3(aq) + NaCl(aq) —> AgCl(s) + NaNO3(aq)

        •ionic equation: Ag+(aq) + Cl-(aq) —> AgCl(s)

        •tests for sulphates (SO4(2-)) with HCL and barium chloride 

        •1. to test for a sulphate ion, add dilute HCL followed by barium chloride solution (BaCl2) 

        •2. a white precipitate means the original compound was a sulphate

                  •the hydrochloric acid was added to remove any trace of carbonate or sulphite ions as both would produce a precipitate, confusing the results - like the halide tests 

              •barium chloride + zinc sulphate —> zinc chloride + barium sulphate

  

              •ionic equation: Ba(2+)(aq) + SO4(2-)(aq) —> BaSO4(s) 

        •hydrochloric acid can detect carbonates

        •1. add dilute HCL to your test sample. If carbonates (CO3(2-)) are present, then CO2 is released (effervescence) since carbonates give off CO2 with HCL

                   •CO3(2-)(s) + 2H+(aq) —> BaSO4(s) 

                            •you can use limewater to test the carbon dioxide