topic 4

• most metals react slowly or not at all w. H20
• heated magnesium reacts w. steam to form magnesium oxide & hydrogen
• How does calcium react with cold water?

  Ca + 2H2O > Ca(OH)2 + H2

  • steadily
  • effervescence (fizzing) when H2 produced
• How does potassium react with cold water?

  2K + 2H2O > 2KOH + H2

  • floats, moves, melts & fizzes
  • h2 burns & lilac flame is seen
• how does sodium react w. cold water?

  2Na + 2H2O > 2NaOH + H2

  • floats, moves, melts & fizzes
• Why do potassium & sodium react similarly to cold water?

  bc they are in the same group (1)
• What metals do not react w. dilute acids?


  copper, silver, gold
• What metals do react violently w. dilute acids?


  sodium, potassium
• what do most metals react w. dilute acid to produce?


  a salt + hydrogen
• Mg(s) + H2SO4(aq) - dilute sulfuric acid ---->

  MgSO4(aq) + H2(g)
• Zn(s) + 2HCl(aq) - dilute hydrochloric acid ---->


  ZnCl2(aq) + H2(g)
• the more reactive the metal, the greater the tendency of the metal atoms to lose electrons to form cations (+ ions)
• Reactivity series above carbon:

  • potassium
  • sodium
  • calcium
  • magnesium
  • aluminium
  • carbon
• Reactivity series below carbon:

  • carbon
  • zinc
  • iron
  • HYDROGEN
  • copper
  • silver
  • gold
• a metal will displace a less reactive metal from its salt solution
• Zn(s) + CuSO4(aq) ---->

  Cu(s) + ZnSO4(aq)
• Zn(s) + CuSO4(aq) > Cu(s) + ZnSO4(aq)

  Why does this reaction produce zinc sulfate solution?

  bc copper is less reactive than zinc "" zinc displaces copper from a copper salt solution

  • copper cannot now replace zinc from the zinc sulfate solution
• displacement reactions are redox reductions
• What is the ionic equation of:

  Mg(s) + ZnCl2(aq) > MgCl2(aq) + Zn(s)

  Mg + Zn (2+) > Mg (2+) + Zn

  • Cl ions are spectator ions as they do not change "" are not in ionic equation
• What is the REDUCTION half equation of:

  Mg + Zn(2+) > Mg(2+) + Zn

  Zn(2+) +2e > Zn

  • metal w. lower reactivity will be reduced
• What is the OXIDATION half equation of:

  Mg + Zn(2+) > Mg(2+) + Zn

  Mg - 2e > Mg(2+)

  • metal which is more reactive will be oxidised
• Reduction:

  gain of electrons

  • removal of oxygen
  • addition of hydrogen
• Oxidation:

  loss of electrons

  • addition of oxygen
  • removal of hydrogen
• an ore is a rock that contains enough of a compound to extract a metal from it for a profit

  • most metals are found like this in Earth's crust
• How are the elements b4 carbon in the reactivity series extracted?

  electrolysis of the molten chloride/oxide

  • large amounts of electricity needed
  • " expensive
• How are zinc, iron, hydrogen, copper extracted?


  by heating w. a reducing agent (e.g. carbon/carbon monoxide) in a blast furnace

  • cheap process bc carbon is cheap & can be source of heat aswell
• How are silver & gold found?

  unreactive metals are found as themselves = native

  • found in Earth's crust as the uncombined elements
• Biological methods of metal extraction (copper):

  copper is trad extracted by heating copper sulfide

  • however copper ores are running low
  • "" we need to extract copper from ores containing much smaller amounts of copper compounds
• Bioleaching:

  uses bacteria grown on a low grade ore

  • bacteria produce a solution containing copper ions (leachate)
  • copper is extracted from this by displacement using scrap iron
  • then purified by electrolysis
  • this method can be used for metals like nickel, cobalt, zinc
• Phytoextraction:


  involves growing plants that absorb metal compounds

  • plants are burnt to form ash, from which the metal is extracted
• ADV for BOTH bioleaching & phytoextraction:

  no harmful gases are produced

  • causes less damage to the landscape than mining
  • conserves supplies of higher grade ores
• DISADV for BOTH bioleaching & phytoextraction:

  very slow
• ADV for bioleaching:

  does not require high temps
• DISADV for bioleaching:

  toxic substances & sulfuric acids can be produced by the process & damage the environment
• ADV for phytoextraction:


  can extract metals from contaminated soils
• DISADV for phytoextraction:

  more expensive than mining some ores

  • growing plants is dependent on weather conditions
• What are the economic implications of recycling metals:

  economically beneficial

  • especially those that are costly to extract (e.g. aluminium)
  • recycling is fast becoming a major industry & provides employment
• mining and extracting metal from ores has detrimental effects on the environment & ecosystems
• Why is it environmentally beneficial to recycle metals?

  more energy efficient to recycle metals than it is to extract them

  • bc melting & re-molding requires less energy
  • saves space at landfill sites & energy in transport
• there is a limited supply of every material on Earth

  • as pop ^ there is a greater need for effective recycling to attain sustainable development