Inorganic chemistry

• The higher up group 7 an element is, the more reactive it is. Group 7 are called the halogens
• As the atomic number of the halogens increases, the elements have a darker colour and a higher boiling point
• At room temperature:

  • chlorine is a fairly reactive, poisonous, green gas
  • bromine is a poisonous, red brown liquid, which gives off an orange vapour at room temperature
  • iodine is a dark grey crystalline solid which gives off a purple vapour when heated
• More reactive halogens will displace less reactive ones
• OILRIG is the pneumonic for reduction and oxidation reactions

  • Oxidation Is Loss, Reduction Is Gain
• Redox reactions involve both oxidation and reduction taking place simultaneously.
• In a redox reaction, electrons are transferred from one reactant to another.
• An oxidising agent accepts electrons and gets reduced, a reducing agent donates electrons and gets oxidised
• In the air there is:

  • 78% nitrogen
  • 21% oxygen
  • 0.04% carbon dioxide
  • 0.96% argon
• When an element is burnt in air it reacts with the oxygen to form an oxide
• Magnesium burns with a bright white flame in air and the white powder that is formed is magnesium oxide which is slightly alkaline when dissolved in water
• Hydrogen burns very easily in oxygen and can be explosive. It has an almost invisible pale blue flame and the only product is water vapour. known as the squeaky pop test
• Sulfur burns in air or oxygen with a pale blue flame and produces Sulfur dioxide, which is acidic when it’s dissolved in water
• If you heat a metal carbonate you get carbon dioxide and a metal oxide. This is an example of thermal decomposition, which is when a substance breaks down into simpler substances when heated
• barrier methods for rust prevention:

  • painting/ coating with plastic - ideal for big and small structures, can be decorative
  • oiling/ greasing - only used when moving parts are involved like on a bike chain
• Sacrificial ways of preventing rust:

  • zinc is more reactive than iron so the zinc will be oxidised instead of the iron
  • a coating of zinc can be sprayed on the object - galvanising
  • big blocks of zinc can be bolted to the iron, used on ships