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All Tests : (Gas Tests (Oyxgen (How is the test carried out? (Place a…

- - - - Place a glowing splint (a split that was recently extinguished but is still glowing hot) inside a test tube with the unknown gas in it.
    - - If oxygen is present, the glowing splint will be relit
    - - Oxygen is vital for life but in high concentrations it will cause things to ignite.
  - - - The lit splint will be extinguished once it is placed inside the test tube if hydrogen is present. It will also make a squeaky pop if the test is positive.
    - - Put a lit splint in a test tube with an unknown gas in it.
    - - Hydrogen can be highly explosive but it's also a great fuel.
  - - - How is the test carried out?
        
        A lit splint is added to the test tube containing the unknown gas
      - What change can be observed for a positive test?
        
        If carbon dioxide is present, the flame will be extinguished
      - Why do we test for this gas?
        
        Carbon dioxide can be poisonous in high concentrations, but it also has lots of uses, e.g. fire extinguishers and fizzy drinks.
    - - How is the test carried out?
        
        Connect two test tubes (one containing your unknown gas and one containing the clear limewater) together via an enclosed tube with a bung on top, and allow the gas to bubble into the limewater.
      - What change can be observed for a positive test?
        
        The lime water will turn cloudy if there is CO2 present
      - Why do we test for this gas?
        
        Carbon dioxide can be poisonous in high concentrations, but it also has lots of uses, e.g. fire extinguishers and fizzy drinks.
  - - - Damp red litmus paper should be inserted into the gas.
    - - If the paper turns blue then ammonia is present. The gas also has a characteristic pungent smell that is quite dangerous.
    - - Ammonia is very important in the manufacture of fertiliser but it's also poisonous.
  - - - Damp UI paper should be inserted into the gas.
    - - If the UI paper turns red and then bleaches, chlorine is present. The gas also has a characteristic sharp smell that is quite dangerous.
    - - Chlorine has lots of industrial uses (e.g. bleaching), but it can be poisonous.
- - - - Result of a positive test
        
        A brown precipitate forms after sodium hydroxide is added
      - Method
        
        Step 3) Wait a few minutes and then record the colour of the precipitate formed
        
        Step 2) Next, using a different pipette, add 5cm3 of sodium hydroxide solution to the test tube
        
        Step 1) Using a clean pipette, fill a test tube with 5cm3 of your unknown sample
    - - Result of a positive test
        
        A blue precipitate forms after sodium hydroxide is added
      - Method
        
        Step 3) Wait a few minutes and then record the colour of the precipitate formed
        
        Step 2) Next, using a different pipette, add 5cm3 of sodium hydroxide solution to the test tube
        
        Step 1) Using a clean pipette, fill a test tube with 5cm3 of your unknown sample
    - - Method
        
        Step 3) Wait a few minutes and then record the colour of the precipitate formed
        
        Step 2) Next, using a different pipette, add 5cm3 of sodium hydroxide solution to the test tube
        
        Step 1) Using a clean pipette, fill a test tube with 5cm3 of your unknown sample
      - Result of a positive test
        
        A green precipitate forms after sodium hydroxide is added
    - - Result of a positive test
        
        If ammonia is present, the red litmus paper should turn blue
      - Method
        
        Step 4) Put a piece of damp red litmus paper into the sample
        
        Step 2) Next, using a different pipette, add 5cm3 of sodium hydroxide solution to the test tube
        
        Step 1) Using a clean pipette, fill a test tube with 5cm3 of your unknown sample
        
        Step 3) Warm the sample (at this point, if it was sodium hydroxide was present it should be giving off ammonia gas)
  - - - Step 3) Dip the clean wire into the hydrochloric acid again, then dip it into the compound.
      - Step 4) Place the wire into the blue flame of a bunsen burner.
        
        Since the blue flame is "colourless" (or at least less so than the orange of the safety flame), the resulting colour will be more accurate as we will be able to tell that the colour came from the cation and not from the bunsen burner. For example, with lithium, if we were to burn it while the flame is on safety, we wouldn't be able to tell if the red colour was just the bunsen burner's colour, or if it was caused by the cation.)
      - Step 2) Place the wire into a blue flame, and ensure that the flame remains colourless
        
        If the wire is placed into the blue safety flame and there is no colour, this means that there are no impurities left on the wire, and that the colour change (if any) later on when the cation is added isn't obstructed or ruined by the wire adding extra colour that could change the results and make them inaccurate.
      - Step 5) Record the colour and then figure out which cation the compound contained.
        
        This can be done by looking at the list below
      - Step 1) Dip the wire into hydrochloric acid.
        
        We do this because we want to clean the wire and remove any impurities.
    - - Potassium (K+)
        
        If potassium is present, the flame will turn lilac
      - Calcium (2+)
        
        If calcium is present, the flame will turn orange-red
      - Sodium (Na+)
        
        If sodium is present, the flame will turn yellow
      - Copper (2+)
        
        If copper is present, the flame will turn green-blue
      - Lithium (Li+)
        
        If lithium is present, the flame will turn red
- - - - Method
        
        Step 2) Add a few drops of the now acidified barium chloride solution to your unknown solution
        
        Step 3) Record the colour of the precipitate (if any) formed
        
        Step 1) Mix some hydrochloric acid with barium chloride solution
      - Result of a positive test
        
        If a white precipitate has formed, then barium sulfate is present
    - - Result of a positive test
        
        If bromine is present, a cream precipitate should have formed
      - Method
        
        Step 2) Next, a few drops of silver nitrate solution are added into the unknown solution
        
        Step 3) Finally, the colour of the precipitate formed should be recorded
        
        Step 1) The unknown sample is first acidified using a few drops of dilute nitric acid
        
        The acidified part is important as this means it reacts with any other ions which could also give a precipitate and mess with the final conclusion of what anion is present in the solution
    - - Method
        
        Add a few drops of hydrochloric acid to your unknown solution
      - Result of a positive test
        
        If bubbles form, then carbonate is present
    - - Method
        
        Step 2) Next, a few drops of silver nitrate solution are added into the unknown solution
        
        Step 3) Finally, the colour of the precipitate formed should be recorded
        
        Step 1) The unknown sample is first acidified using a few drops of dilute nitric acid
        
        The acidified part is important as this means it reacts with any other ions which could also give a precipitate and mess with the final conclusion of what anion is present in the solution
      - Result of a positive test
        
        If chlorine is present, a white precipitate should have formed
    - - Result of a positive test
        
        If iodine is present, a yellow precipitate should have formed
      - Method
        
        Step 2) Next, a few drops of silver nitrate solution are added into the unknown solution
        
        Step 3) Finally, the colour of the precipitate formed should be recorded
        
        Step 1) The unknown sample is first acidified using a few drops of dilute nitric acid
        
        The acidified part is important as this means it reacts with any other ions which could also give a precipitate and mess with the final conclusion of what anion is present in the solution