Topic 4

Cards (35)

  • pH scale

    measure how acidic/alkaline a solution is
  • What can be used to measure the pH
    Universal indicator or a pH probe
  • Titrations

    - used to determine the concentration of an unknown acid or base
  • Titration practical

    WANT TO FIND OUT THE CONCENTRATION OF SOME ALKALI?

    - Using a pipette, add a set volume of a strong alkali to a conical flask.
    - Add a few drops of a SINGLE INDICATOR.
    - add an acid of known concentration in a burette. Do this below eye level to ensure you are not looking up
    - Take an initial reading of the volume of acid in the burette.
    - Gradually add the acid to the alkali using the burette. Make sure that you are regularly swirling the conical flask as you add the acid. As you get closer to the end point, start to add the acid at a slower rate.


    - As soon as the indicator changes colour, stop adding acid.
    - Take a final reading of the volume of acid in the burette.
    - Subtract the final reading from the initial reading to calculate the volume of acid needed to neutralise the alkali.

    The acids and alkali positions could be switched depending on what you need to find
  • Titration apparatus
  • Strong acids in water
    Ionise completely in water
    - all particles dissociate to release H+ ions
  • weak acids in water
    Do not fully ionise in water
    - small proportion of particles dissociate to release H+ ions
  • what is pH
    measure of hydrogen ions concentration
  • Acid + base ->
    salt + water

    neutralisation reaction
  • Are METAL OXIDES and METAL HYDROXIDES acids or bases?
    bases
  • are METAL CARBONATES acids or bases?
    bases
  • Acid + Metal carbonate ->
    salt + water + carbon dioxide
  • How to make salt crystals from an insoluble base: RP
    1) find the correct acid and insoluble base
    2) gently warm the dilute acid using a Bunsen burner, once warmed turn off burner.
    3) add the insoluble base, a bit at a time, until it is in excess.
    4) filter out excess solids
    5) now gently heat the solution in a water bath, until nearly completely evaporated.
    6) leave the solution to cool, usually for a few days.
    7) you can filter if necessary
  • The reactivity series
  • reaction of magnesium and (cold) dilute acid
    - Reacts vigorously
    - lots of bubbles
  • reaction of zinc (or iron) and (cold) dilute acid
    - react slowly when cold
    - more strongly when heated
  • Metal + water ->
    metal hydroxide + hydrogen
  • what is oxidation? (in terms of oxygen and electrons)
    Gain of Oxygen or loss of electrons
  • what is reduction? (in terms of oxygen and electrons)
    loss of oxygen or gain of electrons
  • How are metals extracted by reduction with carbon
    - Metal ore is reduced (loses oxygen)
    - The carbon is oxidised (gains the oxygen)
  • what metals can be extracted by reduction with carbon
    ZINC
    IRON
    COPPER
    metals less reactive than carbon
  • What is a redox rea
    When REDuction and OXidation happen at the same time
  • What is a displacement reaction?
    A reaction in which a more reactive element takes the place of a less reactive element in a compound
  • What happens to the METAL ION in a displacement reaction (in terms of electrons)
    gains electrons
  • what happens to the metal atom in a displacement reaction (in terms of electrons)
    loses electrons
  • Electrolysis apparatus
  • what is electrolysis?

    Electrolysis is the processes that uses electricity to break down ionic compounds into elements
  • Is the Anode POSI
    positive
    (so negative ions form)
  • is the cathode positive or negative?
    negative
    (so positive ions form)
  • Electrolysis results
    ANODE: negative ions - metal less reactive than hydrogen - usually copper

    CATHODE: positive halide ions - or OH+
  • Electrolysis risk assessment

    - wear goggles - stop any substances entering eye
    - wear gloves - stop any harmful chemicals touching skin
    - turn off power supply after usage - ensure no electric shock
  • why cant we use electrolysis on ionic solids
    ions are fixed - can't move
  • Test for chlorine

    litmus paper - bleaches
  • test for oxygen

    glowing splint should relight
  • test for hydrogen

    makes a 'squeaky pop' form a lit splint