Chemistry, 11: Air and water

• To test for waster:

  Add substance to anhydrous copper (II) sulfate solid

  If liquid contains water, the powder will turn into blue hydrated copper (II) sulfate
• How is water purified?

  1. Filter through coarse gravel to remove large pieces of dirt
  2. Filter through beds of fine gravel and sand to remove small particles
  3. Chlorine is passed through to kill bacteria
  4. Water is then supplied to home and industries
• How do you test for water in a substance?

  Add to anhydrous copper (II) sulfate solid

  If it contains water, the powder will turn into blue hydrated copper (II) sulfate

  CuSO4 + 5H2O -> CuSO4.5H2O

  Or

  Add to anhydrous cobalt (II) chloride

  If it contains water, the power will turn into pink hydrated cobalt (II) chloride

  Can be tested with cobalt (II) chloride paper for convenience
• How is water purified?

  1. Water is filtered through coarse gravel to remove large pieces of dirt
  2. It is then filtered through beds of fine gravel and sand to remove small particles
  3. Chlorine is passed through to kill bacteria
  4. It is then supplied to homes and industries
• Air is a mixture of gas that remains fairly constant

  Amount of water vapour can vary around the world
• What is the composition of air?

  78% nitrogen

  21% oxyfen

  0.9% argon

  0.04% carbon dioxide
• What are the common pollutants of air?

  Carbon monoxide

  Sulfur dioxide

  Oxides of nitrogen
• What happens when carbon monoxide is inhaled?

  It can replace the oxygen in haemoglobin in your blood, resulting in less oxygen being carried around in the body.
• What happens when sulfur dioxide mixes with water vapour in air precipitate?

  Creates acid rain that can damage:

  • Vegetation, damages leaves and photosynthesis no longer can take place
  • Soil becomes too acidic to grow crops
  • Buildings and bridges will erode away as the carbonate rocks and metals used to make them has been eroded by the acid rain
• What is the source of carbon monoxide?

  Incomplete combustion of carbon-containing substances
• What is the source of sulfur dioxide?

  Combustion of fossil fuels containing sulfur compounds, leading to acid rain.
• What is the source of nitrogen?

  Car engines
• What is an approach to reducing emissions of sulfur dioxide?

  Can be reduced by:

  • Reducing as much sulfur possible from petrol and diesel at refineries, therefore less sulfur dioxide is emitted when fuels are burnt to run vehicles
  • Flue gas desulfurisation, where waste gas is passed through a scrubber containing calcium oxide. Any sulfur dioxide in the waste gas will react with the calcium oxide to make calcium sulfate which can be removed and used for roads and plaster. Gas leaving will therefore be sulfur free.
• Describe how a catalytic converter removes nitrogen oxide and carbon monoxide from an exhaust emission by reaction over a hot catalyst?


  The catalytic converter is fitted at the end of the car exhaust

  It catalyses the reaction between nitrogen oxide and carbon monoxide, turning them into nitrogen and carbon dioxide

  The equations of the reactions are:2CO + O2 → 2CO22NO + 2CO → N2 + 2CO22NO → N2 + O2
• What is the formation of carbon dioxide?

  Carbon dioxide is produced by the combustion of carbon-containing substances

  Respiration by all living organisms releases CO2 into the air as well

  Carbonates react to produce CO2. During a neutralisation reaction with acid, CO2 is also produced.

  When an acid reacts with a carbonate, CO2 is produced.
• What are the greenhouse gases?

  Carbon dioxide

  Methane
• How does increased concentrations of greenhouse gases cause an enhanced greenhouse effect, contributing to climate change?


  Increased concentration of greenhouse gases traps more heat in the Earth's atmosphere

  When sunlight hits the Earth, some energy is absorbed and warms the surface

  In turn, the Earth emits the energy as infrared radiation.

  GHG in the atmosphere traps some of the infrared radiation, preventing it from escaping into space.

  This leads to a warming of the Earth's surface, contributing to the enhanced greenhouse effect.
• Why do we need NPK?

  Nitrogen (N) needed to make proteins in plants so it can grow

  Phosphorous (P) needed to promote healthy root growth

  Potassium (K) needed for general plant growth
• Describe the displacement of ammonia from its salts?


  Nitrates in fertilisers come from ammonia produced by the Haber process

  • Ammonia can be displaced from its salts by adding an alkali substance
  • Farmers regularly add basic substances such as calcium hydroxide to their soil to neutralise any excess soil acidity
  • If too much of the substance is added or added too soon, ammonia displacement may occur which loses the nitrogen from the fertiliser, reducing the fertiliser effect.
• Describe what is needed in the Haber process:

  • Used to make nitrogen containing fertilisers
  • Requires: Iron catalyst, 450 celcius, 200atm
  • Nitrogen is extracted from the air, via fractional distillation
  • Hydrogen is from natural gas, by reacting methane gas with steam
  • Iron (III) oxide is used as a catalyst
• What is the Haber process:

  • Nitrogen and hydrogen is pressurised at 200atm and heated to 450 celsius
  • Gas is passed over iron (III) oxide
  • Inside a chamber, the nitrogen and hydrogen combine to form ammonia
  • Ammonia is condensed and removed
• What is the equation for the Haber process?

  N2(g) + 3H2(g) ⟷ 2NH3(g)

  It is exothermic