2018

• Crude oil vapour passes up the column.

  Each fraction condenses at a different level
• Why do the fractions separate?

  The fractions have different boiling points
• General formula for alkanes

  $C_nH_{2n+2}$
• test for alkenes

  bromine water
• Why are life cycle assessments done?

  to assess the environmental impact of the stages in the life of a product
• 2 greenhouse gas

  -carbon dioxide

  -methane
• 2 effects of global climate change

  -loss of habitats

  -rising sea levels

  -melting ice
• One way the carbon dioxide emissions can be reduced when a plastic bottle is manufactured

  use recycled plastic
• One pro and one con of using a larger volume

  pro-more accurate result

  con-takes a longer time, more energy is needed to heat more water
• Describe the difference between potable water and pure water

  pure-no dissolved solids

  potable -has dissolved solids
• potable water obtained from

  -groundwater

  -sea water
• Describe how groundwater and seawater are treated to produce potable water

  groundwater-filtered & sterilised

  seawater-distilled or reverse osmosis
• what is a formulation

  A mixture designed as a useful product.
• Explain why potassium chloride has a high melting point

  Giant lattice & is ionic with strong bonds and a large amount of energy needed to overcome
• small things have a larger surface area for the same volume, so more frequent collisions

  Explain in terms of collision theory
• test for chlorine gas

  damp litmus paper -goes white
• How does the equilibrium reach in a reaction

  forward & reverse rates are equal because no escape of reactants or products.
• If a stopper is removed and then replaced, what happens to the equilibrium

  Equilibrium shifts to the right-hand side to produce more of any products, so a new equilibrium will be established.
• Explain how the percentages of nitrogen, oxygen and carbon dioxide in the Earth’s atmosphere today have changed from the Earth’s early atmosphere. (6 marks)A:

  Nitrogen increased

  • Because volcanoes released nitrogen gas into the atmosphere
  • Because denitrifying bacteria produced nitrogen
  • Because ammonia in the atmosphere was converted into nitrogen

  Oxygen increased

  • Because algae and plants evolved and produced oxygen
  • By the process of photosynthesis

  Carbon dioxide decreased

  • Because algae and plants used carbon dioxide during photosynthesis
  • Because oceans formed and carbon dioxide dissolved in the water
  • Because carbon dioxide formed carbonates that precipitated to form sediments and sedimentary rocks
  • Because some organisms formed fossil fuels like coal, crude oil, and natural gas, locking away carbon
• Q: Predict the effect of increasing the temperature on the amount of chlorine gas produced at equilibrium.Explain your answer using Le Chatelier’s Principle. (2 marks)A:

  • The amount of chlorine gas increases
  • Because the forward reaction is endothermic, so the system shifts to oppose the temperature increase by favouring the forward reaction
• Q: Explain the effect of increasing the pressure on this equilibrium. (2 marks)A:

  • There is no change in the position of equilibrium
  • Because there are equal numbers of gas molecules on both sides of the equation (2 mol on each side)