Chapt 11 - QA

• Aqueous sodium hydroxide reacts with aluminium to form a white precipitate of aluminium hydroxide which is soluble in excess sodium hydroxide to form a colourless solution.
• Zinc reacts with sodium hydroxide to form a white precipitate of zinc hydroxide which is soluble in excess sodium hydroxide to form a colourless solution.
• Calcium reacts with sodium hydroxide to form a white precipitate of calcium hydroxide which is insoluble in excess sodium hydroxide.
• Ammonium does not react with sodium hydroxide.
• On heating, ammonia gas is given off from ammonium.
• Ammonia gas turns damp blue litmus paper red.
• Copper(II) reacts with sodium hydroxide to form a light blue precipitate of copper(II) hydroxide which is insoluble in excess sodium hydroxide.
• Iron(II) reacts with sodium hydroxide to form a green precipitate of iron(II) hydroxide which is insoluble in excess sodium hydroxide.
• The precipitate of iron(II) hydroxide turns brown on standing.
• Iron(III) reacts with sodium hydroxide to form a red-brown precipitate of iron(III) hydroxide which is insoluble in excess sodium hydroxide.
• Aluminium

  White precipitate formed is insoluble in excess.

  Zinc

  White precipitate formed is soluble in excess forming a colourless solution.

  Calcium

  No precipitate formed.

  Copper(II)

  Light blue precipitate of copper(II) hydroxide formed is insoluble in excess sodium hydroxide.

  Iron(II)

  Green precipitate of iron(II) hydroxide formed is insoluble in excess sodium hydroxide. The precipitate turns brown on standing.

  Iron(III)

  Red-brown precipitate of iron(III) hydroxide formed is insoluble in excess sodium hydroxide.
• Carbonate can be identified by adding dilute acid and observing effervescence. The gas given off forms a white precipitate of calcium carbonate with limewater. Carbon dioxide is produced in the reaction of carbonate with dilute acid.
• Chloride and Iodide can be identified by adding dilute nitric acid and aqueous silver nitrate, resulting in the formation of a white precipitate of silver chloride and a yellow precipitate of silver iodide respectively.
• Sulfate can be identified by adding dilute nitric acid and aqueous barium nitrate, resulting in the formation of a white precipitate of barium sulfate.
• Nitrate can be identified by adding aqueous sodium hydroxide and a piece of aluminium, then warming the mixture carefully, resulting in the formation of a white precipitate of barium nitrate. The gas given off in the reaction of nitrate with sodium hydroxide turns damp red litmus paper blue. Ammonia gas is produced in the reaction of nitrate with sodium hydroxide.
• Gases

  Hydrogen, Oxygen(n), Carbon dioxide(ac), colourless and odourless

  Chlorine(ac), yellow-green gas with pungent smell

  Sulfur dioxide(ac) and ammonia(al)

  Colourless gas with a pungent smell