Extracting Metals and Equilibria

• What are the products when a metal reacts with cold water?

  Metal hydroxide and hydrogen gas.
• What are the products when a metal reacts with steam?

  Metal oxide and hydrogen gas.
• Equation for calcium reacting with cold water.


  Ca + 2H20 - Ca(OH)2 + H2
• Equation for zinc reacting with steam.


  Zn + H20 - ZnO + H2
• Products when a metal reacts with dilute acids.

  Salt and hydrogen
• Displacement experiment to compare the reactivity of metals.

  Add a solid metal to a salt solution (containing a different metal), if the solid metal is more reactive, it will gradually disappear.
• Why can displacement reactions be called redox reactions?

  The more reactive metal atoms lose electrons to form ions (oxidation) and the less reactive metal ions gain electrons to form the element (reduction).
• Where are most metals extracted from?

  Ores in the Earth’s crust
• What is an ore?

  A rock which contains metals often chemically combined with other substances.
• How do you remove oxygen from a metal core?

  Reduction.
• Reduction with carbon

  Displacement can only occur when the metal is less reactive than carbon.
• How can iron be extracted from its ore?

  Extracted by reduction with carbon.

  2Fe203 + 3C - 4Fe + 3CO2
• How can aluminium be extracted from its ore?

  More reactive than carbon so electrolysis must be used. It must first dissolve into molten cryolite as aluminium oxide has a very high melting point so less energy has to be used when dissolved.
• Phytoextraction

  Plants take up metals through their roots and concentrate them in their shoots and leaves, when burned the metals are removed from the ash.
• Bacterial extraction

  Some bacteria can absorb metal compounds, they produce solutions called leachates that contain the metals. Scrap iron can be used to remove the metal from the leachate.
• Limitations of biological methods of extraction.

  Only suitable for low grade ores with smaller quantities of metals, slow processes, require displacement or electrolysis for the final step.
• How is a metal’s relative resistance to oxidation related to its position in the reactivity series?

  Oxidation is loss of electrons, metals lower in the reactivity series are less reactive so less likely to form cations, making them more resistant to oxidation.
• Advantages of recycling materials.

  Economically beneficial as electrolysis is expensive, prevents detrimental environmental impact from mining and extraction, less waste, less energy, using less finite resources.
• What is a life cycle assessment?

  Analysis of the overall environmental impact that a product may have throughout its lifetime.
• Factors for a life cycle assesment?

  Extraction and processing of raw materials, manufacturing, packaging and transportation, use of the product, disposal.
• What is a reversible reaction?

  A reaction in which the products can react to from the original reactants.
• How can the direction of a reversible reaction be altered?

  By changing the concentration of reactants or products, altering the temperature, or adjusting the pressure.
• Dynamic equilibrium meaning.

  When the rate of the forward reaction is equal to the rate of the backwards reaction, meaning the concentration of reactants and products are constant even though the compounds are continually reacting.
• Why does equilibrium only occur in closed systems?

  No reactants or products escape so they are able to react continuously.
• What is the Haber process?

  An industrial process used to produce ammonia, for making fertilisers.
• Chemical equation for reversible reaction between nitrogen and hydrogen, forming ammonia.


  N2 + 3H2 <=> 2NH3
• Sources for the Haber process.

  Nitrogen - extracted from the air.

  Hydrogen - Obtained from natural gas.
• Conditions for the Haber process.

  450 temperature, 200 atm pressure, iron catalyst
• Effect of increasing the temperature of a reversible reaction if the forward reaction is endothermic.

  Increasing temperature favours the forward reaction as it takes in heat, the equilibrium will shift towards the forward reaction and the yield of the products will increase.
• Effect of increasing the pressure of a reversible gaseous reaction.

  Favours the reaction that produces the least number of molecules, the equilibrium position will shift towards that side.
• Effect of increasing the pressure on a yield of ammonia.

  Shifts the equilibrium to the right as there are fewer molecules of gas, the yield of ammonia will increase.
• Effect of increasing concentration in a reversible reaction.

  The equilibrium will shift to the right so the product yield will increase, reducing the effect of the increased concentration of the reactants.
• If there are equal gaseous molecules of the reactant and product in a reversible reaction what effect will changing pressure have on the equilibrium?

  No effect.