Chemical changes

• What is oxidation and reduction

  Oxidation - gain of oxygen

  Reduction - loss of oxygen
• What product has been oxidised

  Magnesium + Oxygen --> Magnesium Oxide


  magnesium as it has gained oxygen
• What product has been reduced

  Magnesium oxide --> Magnesium + Oxygen


  magnesium as it has lost oxygen
• Name the reactivity series

  Potassium

  Sodium

  Lithium

  Calcium

  Magnesium

  Carbon

  Zinc

  Iron

  Hydrogen

  Copper
• Describe the reactions of the reactivity series with dilute acids

  • Potassium, sodium and lithium - dangerously fast
  • Calcium - extremely vigorous
  • Magnesium - rapid
  • Zinc - quite rapid
  • Iron - quite slow
  • Copper - no reaction
• Describe the reactions of the reactivity series with water

  • Potassium, sodium and lithium - very rapid
  • Calcium - quite rapid
  • Magnesium, zinc, iron and copper - no reaction
• Equation for when an acid reacts with a metal

  Acid + Metal --> Salt + Hydrogen
• Equation for a metal and water

  Metal + Water --> Metal hydroxide + Hydrogen
• What does OIL RIG stand for

  Oxidation

  Is

  Loss of electrons

  Reduction

  Is

  Gain of electrons
• How can metals less reactive than carbon be extracted?

  reduction with carbon
• What is a displacement reaction

  A more reactive element can displace a less reactive element from its compound
• An example of a displacement reaction:

  • Lithium + Magnesium oxide --> Lithium oxide + Magnesium

  Lithium is more reactive so can displace magnesium
• What does acids produce in aqueous solutions


  hydrogen ions
• What is a base

  chemicals which can neutralise acids and produce a salt and water
• What are bases that are soluble in water

  alkalis
• Equation for neutralisation

  hydrogen + hydroxide --> water
• How is water produced in a neutralisation reaction

  between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water
• How can we determine the pH of a solution

  pH probe / universal indicator
• What does the numbers 0-6 represent on the pH scale

  acids
• What does the number 7 represent as on the pH

  neutral
• What does 8-14 represent on the pH scale

  alkalis
• Equation for acids and metal oxides

  Acid + Metal oxide --> Salt + Water
• Equation for acids and metal hydroxides

  Acid + Metal hydroxide --> Salt + Water
• Equation for acids and metal carbonates

  Acid + Metal carbonate --.> Salt + Water + Carbon dioxide
• What does alkalis produce in aqueous solutions


  hydroxide ions
• Explain in terms of gain or loss of electrons which species has been oxidised and which species has been reduced when magnesium reacts with hydrochloric acid

  Magnesium has lost electrons so has been oxidised (Mg to Mg2+) The hydrogen in HCl has gained electrons so has been reduced (H+ to H2 )
• How is a soluble salt formed

  1. React excess acid with insoluble metal oxide
  2. Filter the leftovers
  3. Crystallise the product
• RP8; Making salts

  1. Pour acid into a measuring cylinder then into beaker
  2. Put the beaker over a tripod over a bunsen burner and let it heat gently for a short time
  3. Remove the beaker from the tripod and turn the bunsen burner off
  4. Add a spatula of metal oxide and stir it with a glass rod until it is clear blue
  5. Once it is blue, add more metal oxide until there is excess
  6. The acid has now been neutralised. Filter solution to remove excess metal oxide
  7. Pour the liquid into an evaporating dish and heat it over a water bath
  8. When crystals start to form, turn the heat off and pat it dry
  9. Let if cool
• What are strong acids

  Completely ionised in aqueous solutions
• Examples of strong acids

  • hydrochloric acid
  • nitric acid
  • sulfuric acid
• What is a weak acid

  Partially ionised in aqueous solutions
• Examples of weak acids

  • Carbonic acid
  • Ethanoic acid
  • Citric acid
• What happens to pH as the concentration of hydrogen ions increases

  As the pH scale decreases by one unit, the concentration of the hydrogen ions increases by ten times.
• What is a dilute acid

  A dilute acid will have fewer acid molecules in a given volume than a concentrated acid even if the strength of the acid is the same
• What does the concentration of an acid tell us

  Amount of acid molecules in a given volume of solution
• What is electrolysis

  • Passing an electric current through ionic substances that are molten or in solution to break them down into elements
  • Ions are discharged at electrodes producing these elements
• Describe the reactions taking place at the positive and negative electrodes during electrolysis

  • Positively charged ions move to the negative electrode and the negatively charged ions move to the positive electrode
• Why is electrolysis used to extract some metals

  The metal has to be more reactive than carbon to be extracted by electrolysis otherwise the metal will be extracted by reduction with carbon
• Why is a mixture used as an electrolyte instead of using only aluminium oxide

  The mixture has a lower melting point than aluminium oxide as it has a very high melting point.
• What is the half equation in the extraction of aluminium at the cathode

  Al3+ + 3e- --> Al