Fe 3 Scn 2 Barium Ions example essay topic

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 ( ) IONS - add NaOH to the solution. Iron ( ) is present if a brown iron ( ) hydroxide precipitate is formed. Fe 3+ + OH- Fe (OH) 3 (s) To confirm the presence of iron ( ) ions, add KSC N solution to the ion which should produce a blood red solution if iron ( ) 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.