qualitative analysis - exam qs

• What colour is the potassium flame test?

  Lilac
• What colour is the calcium flame test?

  Orangey red
• What colour is the copper flame test?

  Green
• What colour is the sodium flame test?

  Yellow
• What colour is the lithium flame test?

  Red
• A solution of chloride salt is acidified with dilute nitric acid. Silver nitrate solution is added to the mixture. What is seen?

  A white precipitate is formed
• Example of a salt that is insoluble in water:

  Lead chloride
• What state is sodium chloride?

  Aqueous
• What state is barium sulphate?

  Solid
• Barium salts are toxic. Before some X-rays, patients have to swallow a suspension of barium sulfate, known as a ‘barium meal’. Explain why it is safe for these patients to swallow the barium sulfate:

  Barium sulphate is insoluble so it cannot be absorbed into the bloodstream
• A solution of one salt was made and some dilute nitric acid was added. Drops of silver nitrate solution were added. A yellow precipitate formed, what anion is in the salt?

  Iodide
• A technician wanted to find out which bottle contained the sodium salt and which bottle contained the potassium salt, how?

  Perform a flame test, sodium will give a yellow flame, potassium will give a lilac flame
• When sodium hydroxide solution is mixed with a solution containing copper ions, Cu2+, copper hydroxide, Cu(OH)2 , is formed. Describe what you would see when these solutions are mixed:

  Blue precipitate is formed
• How do you test for ammonium ions?

  Add compound to sodium hydroxide and warm, if the litmus paper turns blue then the test is positive
• Sodium hydroxide solution is added to another solution. A red-brown precipitate is formed. What ion is present in the mystery solution?

  Fe3+
• What substance produces a yellow flame and a white precipitate if dilute HCl and barium chloride are added to it?

  Sodium sulphate
• How do you test if the gas given off is ammonia?

  Moist red litmus paper will turn blue
• How can sodium hydroxide solution be used to distinguish between Fe2+ and Fe3+ ions in solution?

  Fe2+ will make a pale green precipitate. Fe3+ will make a red brown precipitate
• What flame will copper chloride turn?

  Green blue
• How would you use sodium carbonate and copper chloride to produce a pure dry sample of copper carbonate?

  Mix both solutions and a precipitate of copper carbonate will be formed. Filter it out, wash it with water and leave it to dry.