Chemical tests

• Place some hydrochloric acid in a test tube and add a small spatula load of the solid ionic compound. • Look for bubbles of gas. If a gas is released then insert a delivery tube into the test tube and bubble the gas through limewater • If the limewater turns cloudy, carbonate is present • CO3 + 2HCl → Cl2 + CO2 + H2O, with one of the reactant being carbon dioxide, which reacts with limewater to form calcium carbonate which is an insoluble solid • Ca(OH)2 + CO2 → CaCO3 + H2O

• Dissolve a small amount of the solid ionic compound in deionised water (about 3 cm depth). • Add a few drops of nitric acid • Add 1 cm depth of silver nitrate solution

• Dissolve a small amount of the solid ionic compound in deionised water(about 3cm depth) • Add a few drops of hydrochloric acid • Add 1cm depth of barium chloride solution • A white precipitate is formed if sulfate ion is present • SO2-4 + Ba2+ -> BaSO4 Sulfate white solid ion precipitate (High 2- sign low 4 sign)

• Chloride ion - white • Bromide ion - creamy • Iodide ion - yellow • Silver nitrate is AgNO3 • Ag+ + Cl- –> AgCl (white precipitate) • Ag+ + I- –> AgI (yellow precipitate) • Ag+ + Br- –> AgBr (creamy precipitate)

• Turn on a bunsen burner using a match, and then put it on the roaring flame. • Clean a platinum or nichrome wire loop by pouring it into HCl • Put the wire into the bunsen burner, to make sure that there is no flame colour • Put the wire into the substance that is to be tested • Put the wire into the bunsen burner and record the flame colour

Cation name Cation formula Colour of flame Lithium Li+ Red Sodium Na+ Yellow Potassium K+ Lilac Calcium Ca2+ Orange-red Copper Cu2+ Green-blue

Negatively charged ion

Positively charged ion

• Attach a tube from the sample that is to be tested to limewater • If the limewater turns cloudy, carbon dioxide is present • This is because the precipitate calcium carbonate is made • CO2 + Ca(OH)2 -> CaCO3 + H2O, which is how the calcium carbonate is made in the reaction

• Place a lit splint in the test tube that is to be tested • If there is a squeaky pop, hydrogen is present

• Place a glowing splint in a test tube of the substance that is to be tested • If the splint relights, oxygen is present • This is because oxygen is in the fire triangle

Damp red litmus paper in water. Put the solution that is tested in a test tube. Heat the solution with a Bunsen burner to make the solution evaporate and place the litmus paper above the test tube. If Ammonia is present, the red litmus paper will turn blue. This is because Ammonia reacts with water to make ammonium hydroxide which has hydroxide which will turn litmus paper blue.

Put the gas that is to be tested in a test tube. Place a damp blue litmus paper above the test tube. If the litmus paper turns red then white, chlorine gas is present.

Water will boil at 100℃ This can be tested using distillation

Anhydrous copper sulphate turns blue in the presence of water

Testing for cations method 2: Place 5cm3 of copper in one test tube Place 5cm3 of iron (II) solution in another test tube Place 5cm3 of Iron (III) solution in a third test tube Add sodium hydroxide (5 drops using pipette) Observe and record in a suitable table Certain metal ions will react with the hydroxide to form a precipitate The colour of this precipitate identifies the metal ion Cation Colour of precipitate Copper (Cu2+) Blue colour Iron(II) (Fe2+) Green Iron (III) (Fe3+) Orange Cu2+ + 2OH- -> Cu(OH)2 (s) Fe2+ + 2OH- -> Fe(OH)2 (s) Fe3+ + 3OH- -> Fe(OH)3 (s)

NH4(+) + OH(-) –> NH3 + H2O which forms ammonia which can be tested with damp red litmus paper NH3 + H20 –> NH4OH this is alkaline and will turn damp red litmus paper blue

NH4NO3