Displacement Reactions-

• A more reactive halogen can displace a less reactive halogen from solutions of its salts
• For example, chlorine is more reactive than iodine
• Chlorine can displace iodine from potassium iodide solution:

  chlorine + potassium iodide → potassium chloride + iodine

  Cl2(aq) + 2KI(aq) → 2KCl(aq) + I2(aq)
• The reaction mixture turns darker and iodine solution forms
• The slideshow demonstrates what happens when solutions of chlorine, bromine, and iodine are added to various potassium halide salts
• A reactivity series can be produced by attempting displacement reactions
• Different combinations of halogen solution and salt solution are tested
• A halogen cannot displace itself from a solution of one of its salts
• Three tests were not done because a halogen cannot displace itself from a solution of one of its salts
• Balanced equation for the reaction between chlorine and potassium bromide solution:

  Cl2(aq) + 2K+(aq) + 2Br-(aq) → 2K+(aq) + 2Cl-(aq) + Br2(aq)
• Potassium ions, K+, are spectator ions and do not take part in the reaction
• Rewritten equation without spectator ions:

  Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq)
• This equation is a balanced ionic equation
• The balanced equation can be split into two half equations:

  Cl2(aq) + 2e- → 2Cl-(aq) (reduction)

  2Br-(aq) → Br2(aq) + 2e- (oxidation)
• In the reduction half equation, chlorine atoms gain electrons and are reduced
• In the oxidation half equation, bromide ions lose electrons and form molecules, they are oxidised
• Reduction and oxidation happen simultaneously, making the reactions redox reactions
• Displacement reactions and electrolysis reactions are examples of redox reactions