Extracting metals and equilibria

• Oxidation


  The reaction with, or addition of oxygen.
• Reduction


  Removal of oxygen
• Combustion reactions


  • Involve oxidation

  • Always exothermic
• What is an exothermic reaction?

  A chemical reaction that releases heat to its surroundings.
• What is an endothermic reaction?

  An chemical reaction that absorbs heat from its surroundings, resulting in a decrease in temperature.
• Reactivity series


  A table that lists metals in order of their reactivity.
• What does a metal‘s position in the reactivity series compared to carbon dictate?

  How it’s extracted from its ore
• What does hydrogen in the reactivity series show?

  The reactivity of metals with dilute acids.
• What is a dilute acid?

  An acid that has been mixed with water to reduce its concentration
• What is an ore?

  A naturally occurring rock or mineral that contains a valuable metal or element
• What does it mean if a metal is below hydrogen in the reactivity series?

  It’s less reactive than hydrogen and won’t react with dilute acids.
• Because metals at the top of the reactivity series are less resistant to oxidation, they corrode easily. Metals at the bottom are more resistant to corrosion.
• The metals at the top of the reactivity series are the most reactive

  • They easily lose their electrons to form cations

  • They are also oxidised easily
• What is a cation?


  A positively charged ion
• Metals at the bottom of the reactivity series are less reactive

  • They don’t give up their electrons to form cations easily

  • They’re more resistant to oxidation than the metals higher up in the reactivity series
• How can you determine a metal’s position in the reactivity series?

  By reacting it with water and dilute acids.
• The more easily a metal atom loses its outer shell electrons and form a positive ion, the more reactive it will be.
• What is the reaction of metals with water?

  Metal + Water —> Metal Hydroxide + Hydrogen

  ( Or : less reactive metal + steam

  —> metal oxide + hydrogen)
• Metals that react vigorously with water

  • Potassium

  • Sodium

  • Lithium

  • Calcium
• Metals that won’t react with cold water, but will react with steam :

  • Magnesium

  • Zinc

  • Iron
• What metal doesn’t react with water or steam?

  Copper
• Why do some metals react with steam but not cold water?

  They are not reactive enough
• The order of the reactivity series :

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Carbon
  • Zinc
  • Iron
  • Hydrogen
  • Copper
  • Silver
  • Gold
• Other than reacting dilute acids with water, you can directly compare the reactivity of metals using displacement reactions.

  • This involves reacting metals with metal salt solutions
• What is oxidation in terms of electrons?

  Loss of electrons
• What is reduction in terms of electrons?

  Gain of electrons
• Displacement reactions are redox reactions
• What are redox reactions?

  A chemical reaction where oxidation and reduction happen simultaneously
• What happens in a displacement reaction?

  A more reactive element reacts to take the place of a less reactive element in a compound

  • In metal displacement reactions, the more reactive metal loses electrons and the less reactive metal gains electrons.
• What happens to the more reactive metal in a metal displacement reaction?

  It is oxidised
• What happens to the less reactive metal in a metal displacement reaction?

  It is reduced
• What is a compound?

  A substance composed of two or more elements chemically bonded together.
• Metal ore

  A rock which contains enough metal to make it economically worthwhile extracting metal from it.

  • In many cases, the ore is an oxide of the metal.
• • Most of the metals we use are found in their ores in the earth’s crust. The ores are mined and the metals can then be extracted from their ores.

  • Some unreactive metals, such as gold or platinum are present in the Earth’s crust as uncombined elements

  • These metals can be mined straight out of the ground, but they usually need to be refined before they can be used.
• How can a metal be extracted from its ore chemically?

  Reduction using carbon
• What happens when an ore is reduced?

  Oxygen is removed from it
• The position of a metal in the reactivity series determines whether it can be extracted by reduction with carbon

  METALS HIGHER THAN CARBON :

  • Extracted by electrolysis

  • Expensive process

  METALS BELOW CARBON :

  • Extracted by reduction with carbon
• Carbon can only take the oxygen away from metals which are less reactive than carbon itself is.
• Example of reduction using carbon


  Iron oxide is reduced in a blast furnace to make iron.
• When you reduce metal oxides with carbon, you get a mixture of :

  • Carbon dioxide

  • Carbon monoxide