displacement reactions

• the decrease in reactivity is demonstrated by displacement reactions
• full equation:

  Cl2 + NaBr --> Br2 + NaCl
• Half equations:

  reduction - Cl2 (s) + 2e- --> 2Cl- (aq)

  oxidation - 2Br (aq) --> Br2 (s) + 2e-
• overall ionic equation: 2Br- + Cl2 --> Br2 + 2Cl-
• oxidising power: chlorine oxidises bromide ions to bromine
• (aqueous solution)

  NaCl + Cl2

  colourless

  no reaction
• (aqueous solution)

  NaBr + Cl2

  colourless --> orange-yellow

  bromine formed
• (aqueous solution)

  NaI + Cl2

  colourless --> orange-red

  bromine formed
• (aqueous solution)

  NaCl + Br2

  colourless --> orange-yellow

  no reaction
• (aqueous solution)

  NaBr + Br2

  colourless --> orange-yellow

  no reaction
• (aqueous solution)

  NaI + Br2

  colourless --> orange-yellow

  iodine formed
• (organic solvent)

  2NaBr + Cl2 --> 2NaCl + Br2 (yellow layer)
• (organic solvent)

  2NaI + Cl2 --> 2NaCl + I2

  2NaI + Br2 --> 2NaBr + I2

  purple layer