Anions and cations can be identified using a variety of chemical tests. Because some ions produce similar results with one test, other confirmatory tests are essential. ANIONS CARBONATE IONS - add dilute nitric acid If the mixture effervesces (releases CO 2 gas), carbonate ions are present. To test that it is CO 2 gas, preform a limewater test. CO 32- + 2 H+  H 2 CO 3 (s) To confirm the presence of carbonate ions, add a few drops of the solution on to universal paper.

A pH of 8-11 confirms the presence of carbonate ions. CHLORIDE IONS - dissolve the solid in water (nitric acid if insoluble) and add silver nitrate solution If chloride ions are present, a white precipitate of silver chloride forms. Ag+ + Cl-  AgCl (s) To confirm the presence of chloride ions, add NH 3 to the precipitate. The AgCl precipitate should dissolve. PHOSPHATE IONS - add ammonia then Ago 3 solution If phosphate ions are present, a yellow precipitate of silver phosphate forms. PO 43- + 3 Ag+  Ag 3 PO 4 (s) To confirm the presence of phosphate ions, add nitric acid and ammonium molybdate and heat the mixture to about 40˚ C.

The formation of bright yellow precipitate indicates the presence of phosphate ions. SULFATE IONS - dissolve the solid with water (nitric acid if insoluble) and add Ba (NO 3) 2 If sulfate ions are present, a white precipitate will form. Ba 2+ + SO 42- Base 4 (s) To confirm the presence of sulfate ions, dissolve the solid with water (nitric acid if insoluble) and add Pb (NO 3) 2. If sulfate ions are present, a white precipitate of Pb SO 4. CATIONS LEAD (II) IONS - add NaCl If lead (II) is present, a white precipitate of lead (II) chloride forms. Pb 2+ + Cl- P bCl 2 (s) To confirm the presence of lead (II) ions, add KI solution.

If lead is present, a yellow precipitate of lead iodide forms. Pb 2+ + I- PbI 2 (s) COPPER (II) IONS - add sodium hydroxide to the solid If copper (II) ions are present, a blue precipitate forms, some of which dissolves leaving a blue solution. Cu 2+ + OH- Cu (OH) 2 (s) To confirm the presence of copper (II) ions, add to the copper hydroxide precipitate ammonia. The precipitate redissolves to form a deep blue solution. Cu (OH) 2 + NH 3 Cu (NH 3) 34+ +2 OH- IRON (II) IONS - add NaOH to the solid Iron (II) ions are present if a white precipitate forms, which quickly turns brown. To confirm the presence of Fe 2+ Add the solution to acidified KM nO 4.

Fe 2+ is present if it decolourises the potassium permanganate. IRON (III) IONS - add NaOH to the solution. Iron (III) is present if a brown iron (III) hydroxide precipitate is formed. Fe 3+ + OH- Fe (OH) 3 (s) To confirm the presence of iron (III) ions, add KSC N solution to the ion which should produce a blood red solution if iron (III) ions are present. Fe 3+ + SCN- [Fe SCN]2+ BARIUM IONS - add sodium carbonate If barium is present, a white precipitate of barium carbonate forms. Ba 2+ + CO 32- Back 3 (s) Since the formation of a white precipitate indicates the presence of either calcium or barium ions, it is necessary to distinguish e between barium and calcium ions by carrying out a flame test.

Carrying out a flame test on solid barium chloride produces a pale green flame, due to the presence of barium ions. CALCIUM IONS - add sodium carbonate If calcium is present, a white precipitate of calcium carbonate forms. Ca 2+ + CO 32- CaCO 3 (s) Since the formation of a white precipitate indicates the presence of either calcium or barium ions, it is necessary to distinguish between barium and calcium ions by carrying out a flame test. Carrying out a flame test on solid calcium chloride produces a brick red flame, due to the presence of calcium ions.