Chemistry

• describe how metals conduct electricity

  metals have delocalised electrons. the electrons carry electrical charge. The electrons move through the structure
• suggest why alloys do not conduct electricity as well as pure metals.

  in alloys, different sized atoms distort the layers so the movements of delocalised electrons are restricted
• complete half equation for the production of bromine

  BR- -->Br^2 +2E-
• suggest the possible environmental advantages of using PEX instead of copper for hot water pipes

  • less hydrocarbon fuels used
  • no electrical energy is used
  • reduce the need to dig large holes
  • continuous process
• • silver is the best conductor
  • aluminium is the least expensive
  • use aluminium for overhead wires because of its low cost
  • use silver for small uses such as circuit boards
  • copper is also good as it is a good conductor

  
• explain why argon does not form compounds

  atoms of argon have a stable arrangement of electrons so argon atoms do not transfer electrons
• predict the formula of the compound formed between phosphorus and hydrogen

  PH3
• predict whether tellurium reacts with metals

  yes because tellurium is towards the right of the periodic table sp tellurium is a non-metal
• suggest two observations that could be made when barium reacts with hydrochloric acid

  • fizzing
  • temperature increases
• write a balanced symbol equation for the reaction between barium and hydrochloric acid

  Ba + 2HCL----> BaCL2 + H2
• describe how ethene forms poly(ethene)

  many molecules join to form a long hydrocarbon
• PEX is a shape memory polymer. what property does a shape memory polymer have?

  can be deformed but they return to their original shape when cooled
• suggest and explain how the structure of PEX changes this property.

  cross links = extra bonds in PEX

  molecules = chains in PEX are held in position

  molecules = chains in PEX unable to slide past eachother
• Titration required practical


  1. Wear safety goggles

  2. Measure 25 ml of hydrochloric acid A using a pipette and pipette filler

  3. Fill a burette safely with the sodium hydroxide solution

  4. Add a few drops of indicator into the conical flask

  5. Slowly add the alkali, drop by drop, to the conical flask and swirl the flask whilst looking for a colour change

  6. Use a white tile under the flask to help see the colour change

  7. Once a sudden colour change has occurred, stop adding alkali, and record the volume of alkali added from the burette

  8. Repeat this again for the hydrochloric acid B

  9. If the same volume of alkali neutralises the acids, the two acids are of the same concentration
• what is avogrados constant?

  6.02x10^23
• why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

  • Limiting factors
  • some of the products may be lost when seperated from the reaction mixture
  • may not go to completion because it is reversible
• explain why rubidium is more reactive than potassium

  rubidium atom is larger so there is less electrostatic attraction between the nucleus so the outer electron is more easily lost
• explain why titanium costs more than steel

  small amount produced

  takes long to process
• explain why a mixture is used as the electrolyte instead of using aluminium oxide

  mixture has a low melting point than aluminium oxide so less energy is needed
• explain why the positive electrode must be continually replaced

  when the electrode reacts with oxygen. the electrode is carbon so carbon dioxide is produced
• explain why sodium chloride cannot be used as the electrolyte to produce sodium metal

  hydrogen gas would be produced instead of sodium because sodium is more reactive than hydrogen
• name the salt produced by the neutralisation of hydrochloric acid with potassium hydroxide

  potassium chloride