chem higher paper 1

• Explain why the alloy of copper & zinc is harder than pure copper


  • pure copper atoms are all same size so they can slide over each other
  • but zinc atoms are different sizes so they cant slide over each other
• calculate mass of copper in 5.25g

  • %/100 x 5.25
  • 5.25 - ans
  • 4.54
• why is excess copper carbonate used in stage 1 


  • to make sure all acid has reacted w carbonate
• Describe how the student could produce copper sulfate crystals from copper sulfate solution in beaker N 


  • heat it
  • leave in coool place for 24hrs until crystals form
• Why does mass of contents of test tube decrease in mass when copper carbonate is thermally decomposed


  co2 produced escapes
• Compare the structure & bonding of sodium chloride & o2


  • NaCl has giant ionic lattice structure
  • ionic bonding between metal & non-metals
  • strong electrostatic forces between ions
  • o2 is simple covalent bond
  • 2 pairs of electrons shared
• What is meant by strong acid?


  • fully ionises in aq solutions
• what is meant by dilute aq solution?


  • less no. of H+ ions in a large vol.
• How does the hydrogen ion concentration change?


  • decreases by a factor of 100
• Write an ionic equation for the reaction between an acid & alkali


  H+ + OH- -> H2O
• Give two improvements to the method to produce more accurate results


  • fit plastic lid
• Calculate the mass of H that is needed to produce 25g of ammonia


  • mass/mr = 25/17 = ans
  • ans / 2, then x 3 = ans2
  • ans2 x Ar(2) = 4.411...
• Calculate bond energy X for the H-H bond


  • reactants 945
  • products 391 x 6 = 2346
  • 93 + 2346 = 2439 - 945 = 1494
  • 1494/3 = 498
• Name 1 metal that's found in earth as an metal itself


  • gold
• Suggest most economical method for extracting metal z from an oxide of metal z


  • reduction w carbon
• Name substance x shown in figure 10


  • cryolite
• Explain what happens to positive carbon electrodes during extraction of aluminium from aluminium oxide


  • positive electrode is made on carbon
  • reacts w o2 to form c02 which escapes
  • so positive electrode has to be replaced
• Half equation for reaction of negative electrode


  • Al3+ + 3e- -> Al
• Explain why chlorine is more reactive than bromine

  • has fewer electron shells
  • electrons on the outer shell are closer to nucleus
  • stronger force of attraction
  • so easier to gain 1 electron
• Explain why carbon nanotubes can conduct electricity 


  • delocalised electrons r free moving so they can move around structure
  • carry a charge
  • ionic bonding