Reversible reactions

• In reversible reactions, the products can react to produce the original reactants again
• What does ammonium chloride look like?

  White solid
• What is hydrogen chloride?

  A colourless gas
• What does anhydrous mean?

  A substance which doesn't contain any water
• What is the symbol for ammonia?


  NH3
• Why is ammonia important?


  For the manufacture of fertilisers, can be found in cleaning products and is a raw material
• Some ammonia is converted into nitric acid which can be also used for the manufacture of fertilisers and explosives
• How is nitrogen made available for plants?

  Ammonia enables them to build protein molecules
• Why can't plants use nitrogen directly from the air?

  They need nitrogen compounds to be able to absorb them in their roots as it can dissolve in water
• Ammonia is an alkaline gas
• What colour does ammonia turn damp litmus paper?

  Blue
• How can ammonium compounds be identified?


  Heating the solution with sodium hydroxide
• What is the ionic equation for a reaction between ammonium ions and sodium hydroxide?


  NH4 (+) + OH (-) -> NH3 + H2O
• What are the raw materials required in the Haber process for making ammonia?

  Hydrogen and nitrogen
• How can hydrogen be obtained?


  Reacting natural gas (mostly methane) with steam or from cracking in oil fractions
• Where is nitrogen obtained from?

  The air
• What are the 3 conditions needed for the production of ammonia?

  • High temperature = 350-450 degrees+
  • High pressure = 150-200 atm+
  • Catalyst = iron
• What happens to leftover hydrogen and nitrogen in the Haber process?

  They are recycled because the equation is reversible
• What is the ionic equation for the Haber process?


  N2 + 3H2 -> 2NH3

  <-
• How is ammonia obtained in the Haber process?

  1. Hydrogen and nitrogen are pumped into the compressor through pipes after being obtained
  2. Gases are pressurised to 150-200 atm inside the compressor
  3. Pressurised gases are pumped into a tank containing iron catalyst at 350-450 degrees where some hydrogen and nitrogen will react to form ammonia
  4. Unreacted hydrogen, nitrogen and ammonia pass into a cooling tank which liquefies the ammonia. It is then removed into pressurised stroage vessels (expensive)
  5. Unreacted hydrogen and nitrogen gases are recycled
• What happens to the ammonia in the cooling tank?

  Cooled and compressed, causing it to condense into a liquid where it is then separated and removed
• The Haber process is a reversible reaction
• How can the yield of ammonia be changed?

  By changing the pressure and or temperature of the reaction
• What happens if you increase the pressure of the reaction?


  Increases yield of ammonia, but if the pressure becomes too high, it becomes too expensive to be stored by the storage vessels
• What happens if you increase the temperature of the reaction in the Haber process?

  Decreases yield of ammonia
• What happens if the temperature in the Haber process is too low?

  Increases yield of ammonia, but slows the rate of reaction
• Why is a pressure of 200 atm chosen in the Haber process?


  Decent yield, increases rate of reaction
• What would happen if the pressure in the Haber process was higher than 200 atm?

  Higher risk of an explosion
• Why is a temperature of 450 degrees chosen in the Haber process?


  Decent yield, maintains rate of reaction, little reactants are wasted
• Why are compromised conditions used in the Haber process?

  To ensure that there is a decent yield of ammonia, while simultaneously being cost effective and not too expensive
• Why is an iron catalyst used in the Haber process?

  To speed up the reaction
• What happens when the iron catalyst stops working?

  The catalyst is deemed as poisoned, so therefore needs to be replaced regularly
• The most effective fertilisers contain what element?

  Nitrogen - helps plants to produce proteins
• What are the advantages of using fertilisers?


  Increases crop growth and yield and increases quality of soil
• What are the disadvantages of using fertilisers?


  Eutrophication, baby blue syndrome, turns soil acidic
• Most fertilisers are ammonium salts
• What happens in the contact process?

  Used for creating sulfuric acid
• What raw materials are needed for the contact process?

  Sulfur, air and water
• What happens in the first stage of the contact process?

  Sulfur is burned in the air to make sulfur dioxide. It is not a reversible reaction.

  Sulfur + Oxygen -> Sulfur dioxide
• Why shouldn't sulfur dioxide be released into the atmosphere?

  It contributes to acid rain