♡ Topic 4_Extracting metals and equilibria ♡

• Products when a metal reacts with cold water: Metal hydroxide and hydrogen gas
• Products when a metal reacts with steam: Metal oxide and hydrogen gas
• Chemical equation for calcium reacting with cold water: Ca + 2H2O → Ca(OH)2 + H2
• Chemical equation for zinc reacting with steam: Zn + H2O → ZnO + H2
• Products when a metal reacts with a dilute acid: Salt and hydrogen
• Reactivity of a metal that reacts with cold water: Very reactive, as only the most reactive metals can react with cold water
• Reactivity of a metal that reacts with oxygen but not acid or cold water: Not very reactive, as most metals react with oxygen
• Metal that does not react with water, acid, or oxygen: Gold
• Experiment using displacement to compare reactivity of two metals: Add a solid metal to a salt solution. If the solid metal is more reactive, it will displace the metal in the salt solution
• Observation when magnesium is added to copper sulfate solution: Blue solution decolourises and copper coats the surface of magnesium
• Explanation of why a displacement reaction is called a redox reaction: Involves reduction and oxidation in the same reaction
• Reactivity of a metal is related to its tendency to form cations
• Most easily oxidised metals: Metals highest in the reactivity series
• Most metals are extracted from ores found in the Earth's crust
• Ore definition: A rock containing metals chemically combined with other substances
• Metals found in the Earth's crust as uncombined elements: Unreactive metals
• Oxidation in terms of oxygen: Gain of oxygen
• Reduction in terms of oxygen: Loss of oxygen
• Process to extract metal from ores containing oxygen: Reduction
• Methods to extract metals from ores: Reduction with carbon and electrolysis
• Extraction of iron from its ore: By reduction with carbon
• Chemical equation for reduction of iron with carbon: 2Fe2O3 + 3C → 4Fe + 3CO2
• Extraction of aluminium from its ore: By electrolysis
• Dissolving aluminium oxide in molten cryolite: Lowers melting point for electrolysis
• Alternative metal extraction method using plants: Phytoextraction, where plants concentrate metals in their shoots and leaves
• Bacterial extraction:

  • Some bacteria absorb metal compounds
  • These bacteria produce solutions called leachates containing 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
• Oxidation and reactivity series:

  • Oxidation is the loss of electrons
  • Metals lower in the reactivity series are less reactive
  • Less reactive metals are more resistant to oxidation
• Advantages of recycling metals:

  • Economically beneficial because electrolysis is expensive
  • Prevents the detrimental environmental impact of mining and extraction of new metals
  • Less waste produced so less landfill
  • Less energy required compared to electrolysis
  • More sustainable - not using up the finite resources
  • Recycling process provides employment
• Life cycle assessment:

  • Analysis of the overall environmental impact that a product may have throughout its lifetime
  • Factors considered in a life cycle assessment:
  • Extraction and processing of raw materials
  • Manufacturing
  • Packaging and transportation
  • Use of the product
  • Disposal
• Reversible reaction:

  • A reaction in which the products can react to form the original reactants
  • Denoted by the symbol: ⇌
• Dynamic equilibrium:

  • When the rate of the forward reaction equals the rate of the backwards reaction
  • Concentration of reactants and products are constant even though compounds are continually reacting
• Closed system:

  • A system where nothing is added or removed
  • All reactants and products remain in the reaction vessel
• Haber process:

  • An industrial process used to produce ammonia (for making fertilisers)
  • Chemical equation for the reversible reaction between nitrogen and hydrogen, forming ammonia: N2 + 3H2 ⇌ 2NH3
  • Sources of nitrogen and hydrogen for the Haber process:
  • Nitrogen: Extracted from the air
  • Hydrogen: Obtained from natural gas
  • Conditions used for the Haber process:
  • 450°C temperature
  • 200 atm pressure
  • Iron catalyst
• Effect of changing the temperature on a reversible reaction if the forward reaction is endothermic:

  • Increasing temperature favours the forward reaction
  • Equilibrium shifts towards the forward reaction
  • Yield of products increases
• Effect of changing the pressure of a reversible gaseous reaction:

  • An increase in pressure favours the reaction that produces the least number of molecules
  • Equilibrium position shifts towards the side that produces the fewest gaseous molecules
• Effect of decreasing the pressure on the yield of ammonia in the Haber process:

  • Decreasing pressure will shift equilibrium to the left
  • Yield of ammonia will decrease
• Effect of increasing the pressure on the yield of ammonia in the Haber process:

  • Increasing pressure will shift equilibrium to the right
  • Yield of ammonia will increase
• Effect of increasing the concentration of the reactants during a reversible reaction:

  • Equilibrium shifts to the right
  • Product yield increases
  • Effect of increased concentration of reactants is reduced
• Effect of changing the pressure on the equilibrium position if there are equal gaseous molecules of the reactant and product in a reversible reaction:

  • No effect