chemical tests

• Tests for gases include hydrogen, oxygen, carbon dioxide, ammonia, chlorine.
• Test for hydrogen involves using a burning splint held at the open end of a test tube of the gas, which creates a 'squeaky pop' sound.
• Test for oxygen uses a glowing splint inserted into a test tube of the gas, and if the splint relights in oxygen, it indicates the presence of oxygen.
• Test for carbon dioxide involves bubbling the gas through the limewater (calcium hydroxide) and it will turn milky (cloudy).
• Test for ammonia involves making damp red litmus paper turn blue and forming a white smoke of ammonium chloride when hydrogen chloride gas, from concentrated hydrochloric acid, is held near it.
• Test for chlorine involves putting damp litmus paper into chlorine gas, which bleaches the litmus paper and turns it white.
• To carry out a flame test, take a sample of the metal on a wire and put it in a flame, the flame will turn a specific colour, showing what metal it is.
• Colours formed in flame tests for these cations are: Li + , Na + , K + , Ca 2+ , Cu 2+.
• Halide ions can be identified by first adding dilute nitric acid, followed by silver nitrate solution.
• Iron(II) produces a green precipitate.
• The purity of water can be tested by evaporating it on an evaporating dish or by measuring its boiling point.
• Tests for Cl-, Br-, and I- anions can be done using acidified silver nitrate solution, SO42- using acidified barium chloride solution, and CO32- using hydrochloric acid.
• Copper(II) produces a blue precipitate.
• Iodide gives a yellow precipitate.
• Sulfate ions can be identified by first adding dilute hydrochloric acid, followed by barium chloride solution.
• NaOH(aq) forms NH3(g), use damp red litmus paper to test for ammonia gas.
• Chloride gives a white precipitate.
• Anhydrous copper(II) sulfate is white, and when water is present, it turns blue.
• Iron(III) produces a brown precipitate.
• Carbonate ions react with dilute acids to create carbon dioxide, which can be bubbled through limewater to test for its presence.
• A white precipitate will form when sulfate ions are in this solution.
• Bromide gives a cream precipitate.
• Tests for cations NH4+ can be done using NaOH(aq) and identifying the gas evolved, Cu2+, Fe2+ and Fe3+ can also be tested using NaOH(aq).
• Ammonia reacts with nitrogen to form ammonium nitrogen.