ppe rev

• (23) reason why carbon monoxide is difficult to detect [1]

  colourless
• (23) explain why water vapour and and NOT liquid water is produced when diesel burns [2]

  • diesel burns at a high temperature
  • above boiling point of water
• (23) chromatography involves a mobile phase. what’s the other phase? [1]

  stationary phase
• (23) why do the substances in the mixture separate in the mobile phase? [1]

  • different speeds
• (23) in a chromatography experiment, a blue colour moved 4.77cm

  solvent moved 5.3cm

  calculate the Rf value of blue. [2]

  4.37÷5.3= 0.9
• Black ink is a mixture of several colours. Plan an experiment using paper chromatography to:

   • separate the colours in black ink 

  • identify the colours from their Rf values. [6]

  • draw pencil line near the bottom; put small dot on pencil line

  • put a small volume of solvent in a beaker; place paper in the solvent 

  • the dots of ink should be above the level of solvent 

  • put lid on beaker; leave to run 

  • mark solvent front; remove from beaker & let dry 

  • determine Rf values 

  • measure distance of all dots from start line & of solvent front from start line
• (23) Describe how crude oil is separated into fractions. [4]

  • heated to vaporise
  • column gets cooler as you go up
  • fractions condense @ different heights
  • because of different boiling points
• (23) An equation for cracking decane (C10H22) is:

  C10H22(l) → C10H20(l) + H2(g)

  Describe a test to identify the gas produced in the reaction

  • test: burning splint
  • result: makes pop sound
• (23) The student concludes that distilled water is pure.

  Describe a test to confirm that distilled water is pure [2]

  • test: boil at 100 degrees
  • result: freezes at 0 degrees
• (22) Give two errors made by the student.

  Describe the problem each error would cause [4]

  • error 1: line drawn in ink
  • will mix with solvent
  • error 2: solvent above start line
  • ink will dissolve

  
• (22) Give two conclusions the student can make from Figure 2 about the four colours in the brown ink. [2]

  1. blue is most soluble
  2. has an UNKNOWN colour

  
• (22) Why was the green colour still on the start line at the end of the experiment? [1]

  the green colour was insoluble in the solvent

  
• (22) What type of variable is time in this reaction? [1]

  dependent (changes DEPENDING on the independent)

  
• (22) What is the name of the alkane in Figure 6?[1]

  butane (c4h10)

  
• (22) what is a hydrocarbon [1]

  made up of carbon and hydrogen only
• (22) Explain why one of the products of cracking is in high demand [2]

  C2H6 is useful as a fuel (because more) flammable
• (22) After the formation of the Earth’s early atmosphere, the amounts of nitrogen and oxygen in the atmosphere changed.

  Explain the main changes in the amounts of nitrogen and oxygen in the Earth’s atmosphere. [4]

  • nitrogen: increased because of emission from volcanoes
  • oxygen: increased because of photosynthesis
• (22) The combustion of 1.0 kg of coal produces more carbon dioxide than the combustion of 1.0 kg of natural gas.

  Suggest why. [1]

  coal has a higher percentage of carbon
• (22) Metals are extracted from metal ores found in the Earth.

  Describe how bioleaching is used to extract copper from low grade ores [3]

  • uses bacteria
  • to produce solutions containing copper compounds
  • from which copper is obtained by electrolysis