Identifying Compounds

1. Identifying Compounds Definitions Ion: a charged atom Anion: a negatively charged ion Cation: a positively charged ion Tests for Positive Ions Reactions with Sodium Hydroxide • Add Sodium Hydroxide to the solution: • White precipitate = Al, Ca or Mg ions • If warmed and turns red litmus blue = ammonium ions (NH4+) • Coloured precipitate • Light blue = copper • Dirty green = iron (II) • Reddish brown = iron (III)

2. Complete the diagram Unknown solution: add sodium hydroxide solution White precipitate Al3+ dissolves in excess sodium hydroxide Warm through Red litmus turns blue Insoluble in excess sodium hydroxide Coloured precipitate Reddish-brown precipitate Light blue precipitate Ca2+ Dirty green precipitate Mg2+ Tests for Negative Ions Carbonates You can add dilute _____________ _________ to a carbonate. If it fizzes and produces ______ _________ gas, the test is positive. You can check for the gas by using _________ __________ which will go _______. Two carbonates have distinct colour changes when heated Copper Carbonate  Copper Oxide + Carbon Dioxide ( ) ( ) Zinc Carbonate  Zinc Oxide + Carbon Dioxide ( ) ( ) Write balanced word equations for the reactions above: Copper Carbonate: Zinc Carbonate:

3. Halides The Halides are any compound formed with a Halogen e.g. Chlorine, Bromide and Iodide We can add _______ __________ and dilute _______ _____ to a compound to see if it is a halide. The colour of the precipitate tells us which Halide is present: • Chlorine: • Bromine: • Iodine: The general ionic equation for the formation of this precipitate is: Ag+ (aq) + X (aq) AgX (s) Sulfates Sulfates are any compound with a sulfate group (SO4), In solution, they produce a _________ precipitate when we add ___________ ______ followed by __________ _________ solution. The precipitate is the insoluble salt, Barium Sulfate. The ionic equation for this is: Ba2+ (aq) + SO42-  BaSO4 (s)

4. Nitrates Nitrates can be detected by use of the same test we use for ammonium ions: adding sodium hydroxide, __________ the solution through and testing with _______ _________. If no ammonia is given off, we can add a little aluminium powder. This reduces the nitrate ions to ammonium ions, and they can then react with the sodium hydroxide to form _________ gas, which will turn _____ litmus paper ______. Organic substances Organic substances are those which contain mainly _______ in combination with other substances. Inorganic substances are those which consist mainly of other elements, which are not ________. Write a short paragraph explaining how we can detect carbon-carbon (double, C=C) bonds using bromine water. Write a word equation showing the reaction for saturated and unsaturated compounds.