CHEMICAL ANALYSIS

• When do we use flame tests?

  To identify metal ions
• What colour flame does LITHIUM have?

  Crimson (red)
• What colour flame does SODIUM have?

  Yellow
• What colour flame does POTASSIUM have?

  Lilac
• What colour flame does CALCIUM have?

  Brick red
• What colour flame does COPPER have?

  Green
• Which three ions form a white precipitate with NaOH?

  Aluminium

  Calcium

  Magnesium
• Which ions precipitate dissolves when excess NaOH is added?

  Aluminium
• What colour precipitate does COPPER (II) form?

  Blue
• What colour precipitate does IRON (II) form?

  Green
• What colour precipitate does IRON (III) form?

  Brown
• How to form equations for metal hydroxides?

  Cu2+ + 2OH- -> Cu(OH)2

  - You need as many OH- ions as the charge on the metal ion. For example, we have Cu2+ so we need (OH)2 to have the same amount of charge.

  - The Na from NaOH and whatever the metal ion was bonded to will react form a compound together: e.g. CuCl2 +2NaOH -> Cu(OH)2 + 2NaCl
• What do carbonates react with?

  Dilute acids to create carbon dioxide.
• How to identify carbonates?

  The gas can be bubbled through limewater, if the limewater goes cloudy, the gas is C02
• How do you identify a Halide?

  Add dilute nitric acid, follwed by silver nitrate solution.

  (TIP: HOW TO REMEMBER THE HALIDES, Cats With Brains can Ideally Yodel, Chlorine - white, Bromide - cream, iodine - yellow)
• What colour precipitate does CHLORINE have?

  White
• What colour precipitate does BROMIDE have?

  Cream
• What colour precipitate does IODINE have?

  Yellow
• How do you identify Sulfates?

  Add dilute hydrochloric acid, followed by barium chloride solution
• What colour precipitate is formed when sulfate ions are present?

  White
• What are instrumental methods?

  Elements and compounds can be detected and identified using this.

  These are accurate, sensitive and rapid, making them advantageous compared to chemical tests.
• What is flame emission spectroscopy?

  Example of an instruamental method used to analyse metal ions in solutions.
• How does Flame emission spectroscopy work?

  Sample is put into a flame.

  Light given out is passed through a spectroscope.

  Output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations.