Identify the substance oxidised and the substance reduced in the following reaction: MnO₂ + 4HCl → MnCl₂ + 2H…

Question

Identify the substance oxidised and the substance reduced in the following reaction:
 MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
Give a reason for your answer.

Accepted Answer

## Model Answer **Substance oxidised:** HCl (hydrochloric acid) **Substance reduced:** MnO₂ (manganese dioxide) **Reason:** In HCl, hydrogen is oxidised — it loses electrons/hydrogen is removed to form Cl₂. MnO₂ gains hydrogen (is reduced) to form MnCl₂ — it loses oxygen. Thus MnO₂ is the oxidising agent and HCl is the reducing agent. ## Explanation Examiners expect you to name both substances and give a reason based on gain/loss of oxygen or hydrogen. MnO₂ loses oxygen → gets reduced; HCl loses hydrogen (or Cl⁻ gets oxidised to Cl₂) → HCl is oxidised. Always state which is oxidised and which is reduced — one line each — then one reason line. This question tests Section 1.2.5 (oxidation-reduction) concepts.

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