Practicals

• How to distil and test water

  1. Test pH of water using pH meter

  2. If pH is too high, use titration to neutralise it

  3. Use pH meter instead of indicator to prevent contamination

  4. Test water for sodium chloride (main salt in seawater)

  5. Sodium: Perform flame test, if present it will turn yellow

  6. Chloride: Add dilute nitric acid and silver nitrate solution, if present white precipitate will form

  7. Pour salty water into distillation apparatus, heating flask meaning water will boil and evaporate leaving salt behind and water condenses into water and can be collected

  8. Retest pH and sodium chloride presence
• Concentration of HCl reacting with Mg to make H2:

  • add set volume of dilute hydrochloric acid to conical flask, place on mass balance

  • add magnesium ribbon to acid and quickly plug with cotton wool

  • start the stopwatch and record mass, then take regular reading of mass

  • repeat with with more concentrated acid solutions
• Concentration of HCl reacting with sodium thiosulfate to produce cloudy precipitate:

  • add set volume of dilute sodium thiosulfate to conical flask and place on peice of paper with black cross on

  • add some dilute HCl to flask and start stopwatch

  • watch the black cross disappear and time how long it takes to go

  • repeat with different HCl concentrations
• How do you test for chlorine?

  bleaches damp litmus paper
• How do you test for oxygen?

  relights glowing splint
• How do you test for carbon dioxide?

  shake with calcium hydroxide (limewater) will turn cloudy
• How do you test for hydrogen?

  lit splint wll make ' squeaky pop ' sound
• How do you identify carbonates?


  add drops of dilute acid to sample and connect test tube to test tube of limewater, should turn cloudy if present
• How do you identify sulfates?


  add drops of dilute hydrochloric acid and barium chloride solution and if present white precipitate should form
• How do you identify halides?


  add drops of dilute nitric acid and silver nitrate solution if present:

  -> chloride forms white precipitate

  -> bromide forms cream precipitate

  -> iodine forms yellow precipitate
• How do you do the flame tests?

  • cleaning a platinum wire loop by dipping it in some dilute HCl then holding it in a blue bunsen burner flame until it burns with no colour

  • dip loop into sample and put in flame

  • observe the colour and record
• What colour do the following metals turn in the flame test?

  • lithium - crimson

  • sodium - yellow

  • potassium - lilac

  • calcium - orange-red

  • copper - green
• What do you react metals with to make coloured precipitates?

  sodium hydroxide
• What colour precipitates do the following metals form when reacted with sodium hydroxide?

  • calcium - white

  • magnesium - white

  • aluminium - white, redissolves in excess to form colourless

  • copper - blue

  • iron (III) - brown

  • iron (II) - green
• What are the 3 ways of measuring react of reaction?

  • precipitation and colour change

  • change in mass (given off)

  • volume of gas given off - gas syringe