Oxidation, reduction and disproportionationEdexcel A-Level Chemistry: Mind map

Exam questions on Oxidation, reduction and disproportionation

1. A teacher demonstrates two reactions of s- and p-block elements: magnesium ribbon burning in oxygen, 2Mg + O₂ → 2MgO, and sodium burning in chlorine, 2Na + Cl₂ → 2NaCl.
   Explain, in terms of electron transfer, why magnesium acts as a reducing agent in its reaction with oxygen.2 marks
2. Chlorine gas is bubbled through aqueous potassium bromide. The solution turns orange as bromine forms. The ionic equation is Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂.
   Use oxidation numbers to show that this is a redox reaction.2 marks
3. Chlorine is used to disinfect swimming pool water. When it dissolves in water it forms chloride ions and chlorate(I) ions, ClO⁻, which kill bacteria.
   The reaction of chlorine with water is Cl₂ + H₂O → HCl + HClO. Use oxidation numbers to explain why this is a disproportionation.3 marks