Chemical Reactions

• what are 3 ways to spot a redox reaction?

  1. Gaining or losing electrons (e.g. combustion, corrosion, extraction of metals)
  2. Gain or loss of electrons (e.g. electrolysis)
  3. Change in oxidation number [the state of an element or compound is decreased] (e.g. displacement and combination reactions, metal+acid)
• what are the rules for oxidation number?

  ON refers to a single atom or ion which can be on its own or in a compound

  • the ON of compound and element = 0
  • the ON of an ion is equal to the charge of the ion (e.g. F- = -1)
  • the ON of oxygen in a compound is always -2

  In addition

  • if the ON increases, oxidation has occurred
  • if the ON decreases, reduction has occurred
• what is an oxidising agent?

  A substance that oxidizes another substance, in doing so becomes itself reduced.

  • gains electrons as another substance loses electrons
  • ex: hydrogen peroxide, fluorine and chlorine
• what is a reducing agent?

  a substance that reduces another substance, in doing so becomes itself oxidised

  • loses electrons as another substance gains electrons
  • ex: carbon and hydrogen

  The process of reduction is very important in the chemical industry as a means of extracting metals from their ores