Chemical changes

• alkalis

  • form Hydroxide (OH-) ions when they dissolve
  • type of base
  • greater than a ph of 7
• acids

  • form Hydrogen (H+) ions when they dissolve
  • less than a ph of 7
• oxidation

  • gaining oxygen
  • losing electrons
  • metal + oxygen = metal oxides
• reduction

  • losing oxygen
  • gaining electrons
  • metal oxides lose oxygen and goes back to original form
  • metal oxide = metal
• Redox reactions:

  $Mg(s) +$$2H+$$(aq) +$$2Cl-(aq) → Mg2+$$(aq) +$$2Cl-(aq) +$$H2(g)$

  Mg is being oxidised(lost 2 electrons) and H is reduced (gained an electron each)
• The easier it is for a metal to form its positive ion, the more reactive the metal is
• reactivity series

  
• reactivity series

  1. potassium- please
  2. sodium- send
  3. calcium- cats
  4. magnesium- monkeys
  5. aluminium- and
  6. carbon- cute
  7. zinc- zebras
  8. iron- into
  9. hydrogen- hot
  10. copper- countries
  11. silver- signed
  12. gold- gordon
• What is produced when reactive metals react with cold water?

  Metal hydroxides

  hydrogen
• extraction of metals

  • metals less reactive that carbon can be extracted by carbon
  • carbon is cheap and abundant
• metals that react with dilute acids but not cold water?

  • magnesium
  • aluminium
  • zinc
  • iron
  • lead
• What type of reaction is used when extracting metals using carbon?

  reduction
• metal + water = metal hydroxide + hydrogen
• metal + acid = metal salt + hydrogen
• In a reduction reaction with carbon, a metal oxide loses oxygen and gains electrons to form a pure metal.
• metal carbonate + acid = metal salt + water + carbon dioxide
• metal oxide + carbon = metal + carbon dioxide
• What are the products of the reaction between copper oxide and sulfuric acid?

  copper sulfate crystals

  water
• weak acids only partially ionise in water

  not all the acid molecules break up to form hydrogen ions
• strong acids fully ionise in water

  all acid molecules break up to form hydrogen ions
•  The more substance dissolved in a solvent the more concentrated it is
• The pH of lemon juice is about 2, whereas tomato juice's pH is about 4. Approximately how much of an increase in hydrogen ion concentration is there between tomato juice and lemon juice?

  x100
• Ionic compounds that dissolve in water to make a solution that conducts electricity are called electrolytes
• Positively charged ions (cations) move to the negative electrode (cathode).
• Negatively charged ions (anions) move to the positive electrode (anode).
• What happens when we electrolyse MOLTEN copper oxide (CuO)?

  copper ions are positively charged so are attracted to the cathode and gain electrons (reduction)

  negatively charged oxygen ions are attracted to the anode and lose electrons (oxidation)
• carbon dioxide is formed at the anode (+) because it is made from carbon
• electrolysis

  • lots of energy needed
  • expensive
• Electrolysis of AQUEOS Solutions- cathode (-)

  • if the metal is more reactive than hydrogen, hydrogen is produced
  • if the metal is less reactive, the metal is produced
• Electrolysis of AQUEOS Solutions- anode (+)

  • if halide ions are present (fluoride, chlorine, bromide, iodine), the halogen forms
  • if halide ions are absent, oxygen forms
• What characterises a more reactive metal?

  a metal that forms a positive ion more easily