Chemical Tests

• Flame Test Results

  Li+ = Red

  Na+ = Yellow

  K+ = Lilac

  Ca(2+) = orange - red

  Cu(2+) = blue - green
• What do you clean the nichrome wire with in a flame test?

  Hydrochloric acid
• Sodium Hydroxide Test

  • For this test, you add a few drops of sodium hydroxide solution yo a solution of your mystery compound.
  • If a hydroxide precipitate forms, you can use it’s colour to identify which metal ion was in the compound.
• Sodium Hydroxide Results

  Cu(2+) = light blue precipitate

  Fe (ll) = green precipitate

  Fe (|||) = red brown precipitate
• Testing for Ammonium Ions + Testing for Ammonia Gas

  Testing for Ammonium ions

  1. To find out whether a substance contains ammonium, all you need to do is add some sodium hydroxide solution to your mystery substance and heat it gently.

  → If ammonia gas is given off, it means ammonium ions are present in the substance.

  1. To test for ammonia, hold a piece of damp red litmus paper on the mouth of the tube → if ammonia is present it will turn blue.
• Testing for Halide Ions

  Halide ions include chloride, bromide and iodide - all of which produce a precipitate that prove their existence.
• Testing for Halide Ions

  Firstly, add some dilute nitric acid to your substance. This acid is added first to get rid of any carbonate ions - they produce a pale precipitate that can confuse tests.

  • ( Can not use HCI, because you’d be adding chloride ions. )
  • Then add a few drops of silver nitrate solution.
• Halide Ions Result

  • Chloride gives a white precipitate when silver chloride is formed.
  • Ag+ + Cl- -> AgCl
  • Bromide gives a cream precipitate when bromide silver is formed
  • Ag+ + Br- -> AgBr
  • Iodide gives a yellow precipitate when iodide silver is formed.
  • Ag+ + I- -> AgI
• Carbonate Ions Test

  To test for (CO3)2-, add some dilute acid -> (HCI)

  • If carbonate ions are present, the mixture will fizz because the carbonate will react with acid to produce CO2
  • You can check to see if gas is produced is CO2 by bubbling it through limewater. It will turn cloudy if it is present.
• Testing for Sulfate Ions

  • First add some dilute HCI to the test sample - this stops any precipitation reactions from taking place NOT involving sulfate ions.
  • Then add barium chloride solution. If sulfate ions in the solution, a white precipitate of barium sulfate will form.
• Physical Test for Pure Water

  • A physical test to see if a sample of H2O is pure is to check their boiling point.
  • Any impurities present will usually tend to raise the BP and depress the melting point of pure substance
• Test for Water

  • Anhydrous Copper (||) sulfate turns white to blue on the addition of water
• Chlorine

  Put damp blue litmus paper on a boiling tube - paper is bleached.
• Hydrogen

  Hold a lighted splint in mouth of test tube -> burns with a squeaky pop sound.
• Oxygen

  Hold a glowing splint -> the splint will relight.
• Chemical Symbols

  (CO3)2- -> carbonate

  (SO4)2- -> sulfate

  (NH4)+ -> ammonium ions

  (NH3) -> ammonia gas

  (NO3)- -> nitrate