pmt flashcards

• 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 + hydrogen gas
• chemical equation for when calcium reacts with cold water 


  $Ca +$$2H2O -> Ca(OH)2 +$$H2$
• chemical equation for when zinc reacts with steam 


  $Zn +$$H2O -> ZnO +$$H2$
• what are the products when a metal rects with a dilute acid?


  salt + hydrogen
• if a metal reacts with cold water, what does it suggest about the reactivity of this metal?

  • metal is very reactive as only most reactive metals react with cold water
• how reactive is a metal if it reacts with oxygen, not acid or cold water

  • not very reactive, most metals react with oxygen
• name a metal which will not react with water, accidents or oxygen


  gold
• describe an experiment that uses displacement to compare the reactivity of two metals

  1. add a solid metal to a salt solution (salt must contain a different metal)
  2. if solid metal = more reactive-> will gradually disappear, displacing the meta that was in the salt solution
  3. if nothing happens: metal in salt = more reactive and cannot be displaced
• what would be observed when magnesium is added to copper sulfate solution?

  • copper sulfate solution= blue
  • magnesium= more reactive than copper
  • when magnesium = added, the blue solution decolourises + copper coats the surface of the magnesium
• why can a displacement reaction be called a redox reaction? Explain in terms of electron transfer

  • redox reaction occurs when reduction + oxidation are taking place in the same reaction
  • displacement reaction: more reactive metal atoms lose electrons to form ions (oxidation) + less reactive metal ions gain electrons to form an element (reduction)
• what is a redox reaction?

  • when reduction + oxidation takes place in the same reaction
• the reactivity of a metal is related to its tendency to form...


  cations (positive ions)
• which metals are most easily oxidised?

  • metals highest in the reactivity series
  • more reactive metals = more likely to react with water + dilute acids to form cations
• where are most metals extracted from?


  from ores found in the Earth's crust
• what is an ore?


  A rock that contains metals often chemically combined with other substances
• which metals are found in the earth's crust as uncombined elements?


  unreactive metals
• explain what oxidation means in terms of oxygen?


  gain of oxygen
• explain what reduction means in terms of oxygen?


  loss of oxygen
• Most ores contain metals chemically combined with oxygen. What process must be carried out to extract the metal?

  • most ores contain metals chemically combined with oxygen
  • reduction must be carried out
• what two methods could be used to extract metals from their ores?

  • reduction with carbon- only be done if metal= less reactive than carbon
  • electrolysis- can be done with all metals, but requires a large amount of energy (high cost £)
• how would you extract iron from its ore?

  • iron= less reactive than carbon so can be extracted by reduction with carbon
  • electrolysis can be used but would use unnecessary energy (high cost £)
• what is the chemical equation for the reduction with carbon?


  $2Fe2O3 +$$3C -> 4Fe +$$3CO2$
• how can aluminium be extracted from its ore?

  • aluminium= more reactive > carbon so electrolysis
  • when the molten ore undergoes electrolysis, the metal forms at the cathode
• when aluminium = extracted from aluminium oxide, why is it first dissolved in molten cryolite?

  • aluminium oxide has a very high melting point
  • dissolved in molten cryolite to produce an electrolyte with a lower melting point
  • reducing energy usage + cost
• How can plants be used as an alternative metal extraction method?

  • phytoextraction
• How can plants be used as an alternative metal extraction method- how does it work?

  • phytoextraction: plants are grown in areas with metals in the soil
  • plants take up metals through roots + concentrate them in their shoots + leaves
  • plants then burned + metals removed from ash
• how can bacteria be used as an alternative metal extraction metal?


  bacterial extraction
• how can bacteria be used as an alternative metal extraction metal? how does it work?

  • bacterial extraction: some bacteria absorb metal compounds
  • bacteria produce solutions called leachates containing metals
  • scrap iron can be used to remove the metal from the leachate
• what are the limitations of biological methods of extraction?

  • only suitable for low grade ores with smaller quantities of metals
  • slow processes
  • require displacement for electrolysis for the final step
• how is a metal's relative resistance to oxidation related to its position in the reactivity series?

  • oxidation= loss of electrons
  • metals lower in the reactivity series = less reactive
  • means they are less likely to form cations so are more resistant to oxidation
• what are the advantages of recycling metals?

  • economically beneficial: electrolysis = expensive
  • less waste produced= less landfill
  • less energy required compared to electrolysis
  • prevents detrimental environmental impact of mining and extraction of new metals
  • more sustainable- not using up finite resources
  • recycling process provides employment
• what is a life cycle assessment?

  • analysis of overall environmental impact a product may have throughout its lifetime
• what factors does a life cycle assessment of a product consider?

  • extraction + processing of raw materials
  • manufacturing
  • packaging + transportation
  • use of the product
  • disposal
• what is a reversible reaction?

  • reaction in which products can react to form the original reactants
• how can the direction of a reversible reaction be altered?


  changing the reaction conditions

  • temperature
  • pressure
  • concentration
• what is meant by the term dynamic equilibrium?

  • when the rate of the forward reaction equals the rate of the backwards reaction
  • means concentration of reactants and products are constant even though compounds are continually reacting
• what is a closed system?

  • a system where nothing is added or removed
  • all reactants + products remain in the reaction vessel
• why is equilibrium only reached if the reaction takes place in a closed system?

  • closed system prevents any reactants + products from escaping
  • therefore: able to rect continuously
• What is the Haber process?

  • an industrial process used to produce ammonia (for making fertilisers)