topic 5

• What are the properties of transition metals?

  shiny, malleable, strong, high melting point, ductile, conduct heat and electricity, colourful compounds, make good catalysts
• Give examples of transition metals being used as catalysts

  Iron is the catalyst in the Haber Process

  Vanadium Peroxide is used is making sulphuric acid in the contact process
• What is the colour of most compounds containing iron (Fe2+)?

  green
• What is the colour of most compounds containing copper?

  blue
• What is the colour of most compounds containing iron (Fe3+) ?

  orange/brown
• What are alloys?


  substances made from two or more different metals mixed together
• Why are alloys harder than pure metals?

  the different sized atoms of the metals disrupt the layers in the structure, making it more difficult for them to slide over each other
• What is bronze made from, and its uses?

  Copper and Tin

  Used to make medals, decorative ornaments and statues
• What is brass made from, what are its uses?

  brass is more malleable than bronze

  it is made from copper and zinc

  used in situations where lower friction is required, like taps and door fittings
• What are gold alloys used for? What metals are mixed with gold for this purpose?

  jewellery

  zinc, copper and silver are used to strengthen it
• What are aluminium alloys used for?

  To make aircraft

  Pure aluminium is not strong enough, so it must be mixed with other metals to increase its strength
• What is rusting?


  The corrosion of iron due to the reaction of iron with air in the presence of water
• What is corrosion?


  The destruction of materials by chemical reactions with substances in the environment - oxygen and water are needed
• What methods prevent corrosion?

  Painting, oiling, greasing, sacrificial protection and galvanising
• What is sacraficial protection?

  When a more reactive metal is attached to an object to prevent corrosion, because the oxygen and water will react with it instead
• What is galvanising?


  Galvanising can be used to protect iron or steel objects. The object is coated in a layer of zinc, the zinc stops water and oxygen reaching the initial metal and stops corrosion
• What is electroplating?


  The process of depositing a thin layer of metal on an object during electrolysis.
• During electroplating, is the object being coated the anode or the cathode?

  cathode
• What is the formula for concentration (with moles)?

  concentration = moles/ volume

  volume must be in dm^3
• What is the formula for molar volume?

  molar volume = gas volume/ number of moles
• How many dm^3 does one gas mole take up at room temp and pressure?

  24 (24,000 cm^3)
• What is the formula for atom economy?

  % atom economy = ( mass of desired product / total mass of reactants )x 100
• What is atom economy?

  Atom economy is a measure of the proportion of reactant atoms that become part of the desired product (rather than by-products) in the balanced chemical equation.
• What is the formula for percentage yield?

  percentage yield =( actual yield/theoretical yield) x 100
• What is the formula for the Haber Process?

  N2(g) + 3H2(g) --> 2NH3(g)
• What is produced in the haber process?

  ammonia
• Describe the conditions of the Haber Process

  the reactants are passed over an iron catalyst at a temperature of 450C and a pressure of 200atm
• What would be ideal conditions for the haber process?

  Very high pressure, and very low temperature
• Why can't a low temperature be used in the haber process?

  Rate of reaction would be too slow
• Why can't a really high pressure be used in the haber process?

  It would be too expensive to achieve
• What are the main elements needed in fertilisers?

  Phosphorus, nitrogen and potassium
• How can ammonium sulfate be prepared in a laboratory?

  1) add ammonium solution to a conical flask with some methyl orange indicator

  2) slowly add dilute sulphuric acid from a burette until to colour changes from orange to red

  3) repeat without the indicator

  4) evaporate the solution and leave to crystallise then filter out the ammonium sulphate crystals and leave them to dry
• What are fuel cells?

  Fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen or air. The fuel is oxidised electrochemically within the fuel cell to produce a potential difference.

  The overall reaction in a hydrogen fuel cell involves the oxidation of hydrogen to produce water.
• What are the advantages of hydrogen fuel cells?

  They produce water, which is not a pollutant, they are lightweight and small, they have no moving parts so are unlikely to break down, fewer stages in the process, so less energy lost via heat
• What are the disadvantages of hydrogen fuel cells?

  - hydrogen is highly flammable so hard to store

  - hydrogen is sometimes produced for the cell by non-renewable sources

  - hydrogen is difficult to store