Identifying Compounds Definitions Ion: a charged atom Anion: a negatively charged ion Cation: a positively charged ion Tests for Positive Ions Element Colour Lithium Sodium Barium Potassium Calcium Flame test colours Li – bright red Na – golden yellow Ba – green K – lilac Ca – brick red Tell the difference between Al, Ca and Mg Keep adding H2SO4, if the precipitate dissolves, the compound contains Al ions Ca and Mg can be distinguished by flame tests – Ca gives a brick red colour, Mg no colour at all 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)

Tests for Negative Ions Complete the diagram Unknown solution: add sodium hydroxide solution White precipitate Al3+ dissolves in excess sodium hydroxide Insoluble in excess sodium hydroxide Ca2+ Mg2+ Light blue precipitate Dirty green precipitate Reddish-brown precipitate Warm through Red litmus turns blue Coloured precipitate 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:

Ag+ (aq) + X (aq) AgX (s) 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)

Nitrates Organic substances 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.