Topic 3 - Redox I

• An oxidising agent is reduced, a reducing agent is oxidised
• A disproportionation reaction is when a reactant is both oxidised and reduced
• A redox reaction is a reaction that involves both reduction and oxidation
• Oxidation is the loss of electrons
• Reduction is the gain of electrons
• The oxidation number of an element is always zero
• The sum of oxidation numbers in a compound is always zero unless a charge is given
• The more electronegative element in a substance is given the negative oxidation number
• The oxidation number of fluorine is always -1
• The oxidation number of hydrogen is +1 except when combined with a less electronegative element, then it's -1
• The oxidation number of oxygen is always -2, except in peroxides when it's -1 and when combined with fluorine when it's +1
• When an element is oxidised, oxidising number increases
• When an element is reduced, the oxidising number decreases
• The oxidation number of some elements in compounds will be written as roman numerals in brackets
• When writing full equations from half equations you can:

  • Add H+ to have more hydrogens
  • Add H2O to get more oxygens
  • Add electrons to balance charges
• Reducing agents are electron donors
• Oxidising agents are electron acceptors
• To combine 2 half equations, they must be balanced in atoms and charge