Weekly a level chemistry video now uploaded to YouTube. How to do the overall equation and the nucleophilic addition elimination...

Sulphuric Acid is reduced by Iodide ions to form Sulphur Dioxide. Iodide ions are oxidised to Iodine. Reduction Half Equation H₂SO₄ -----> SO₂ 1. Balance the species that has been oxidised or reduced. In this case the sulphur has been reduced from +6 to +4. The sulphur atoms are balanced. 2. Balance oxygen using H₂O There are 4 on LHS and 2 on RHS so add 2 H20 to the RHS H₂SO₄ ----> SO₂ + 2 H₂O 3. Balance hydrogen atoms (H+) There are 2 on LHS and 4 on RHS