RP07 - Identifying Ions

• What is the first step in carrying out a flame test to identify metal ions?

  Clean a platinum wire loop by dipping it in HCl and then holding it in the blue flame until it burns without any colour
• What is the second step in carrying out a flame test to identify metal ions?

  Dip the loop into the sample you want to test and put it into the blue flame of the Bunsen burner
• What is the third step in carrying out a flame test to identify metal ions?

  Record the colour of the flame
• What precaution should you take when using a Bunsen burner?

  Don't leave unattended
• What precaution should you take when using a Bunsen burner?

  Turn off gas or leave on orange safety flame when not in use
• What precaution should you take when using a Bunsen burner?

  Tie back long hair
• What precaution should you take when using a Bunsen burner?

  Keep flammable chemicals away from the flame
• What colour flame is produced by lithium ions?

  Crimson
• What colour flame is produced by sodium ions?

  Yellow
• What colour flame is produced by potassium ions?

  Lilac
• What colour flame is produced by calcium ions?

  Orange-red
• What colour flame is produced by copper ions?

  Green
• Why must the wire be cleaned before carrying out a flame test?

  To remove any unwanted ions that might obscure the colour of the flame
• Why can a flame test not be used when a compound contains a mixture of metal ions?

  The flame colours of some ions may be hidden by the colours of other metal ions
• How can you test for carbonate ions?

  Add a few drops of HCl to the sample in a test tube, connect this test tube to a test tube of limewater, and if carbonate ions are present, carbon dioxide will be produced causing the limewater to turn cloudy
• What is the chemical equation for the reaction between HCl and Na2CO3?

  $Na_2CO_3 +$$2HCl \rightarrow CO_2 +$$2NaCl +$$H_2O$
• How can you test for sulfate ions?

  Add HCl to remove any CO3^2- ions, then add a couple of drops of barium chloride, and if sulfate ions are present a white precipitate of barium sulfate will form
• What is the chemical equation for the reaction between BaCl2 and MgSO4?

  $BaCl_2 +$$MgSO_4 \rightarrow BaSO_4 +$$MgCl_2$
• How do you carry out a test for halide ions?

  Add a couple of drops of nitric acid to react with any carbonate ions, then add a couple of drops of silver nitrate and observe the colour of the precipitate
• What colour precipitate is formed when silver nitrate is added to a chloride solution?

  White
• What colour precipitate is formed when silver nitrate is added to a bromide solution?

  Cream
• What colour precipitate is formed when silver nitrate is added to an iodide solution?

  Yellow
• What colour precipitate forms when sodium hydroxide reacts with calcium ions?

  White
• What colour precipitate forms when sodium hydroxide reacts with copper(II) ions?

  Blue
• What colour precipitate forms when sodium hydroxide reacts with iron(II) ions?

  Green
• What colour precipitate forms when sodium hydroxide reacts with iron(III) ions?

  Brown
• What colour precipitate forms when sodium hydroxide reacts with aluminium ions?

  White, which redissolves with excess NaOH to form a colourless solution
• What colour precipitate forms when sodium hydroxide reacts with magnesium ions?

  White
• How can you identify which solution contains aluminium ions and which contains magnesium ions?

  Add excess sodium hydroxide. Both will form white precipitates but the one containing aluminium ions will redissolve to form a colourless solution.