Catalysts

• What is autocatalysis?

  Autocatalytsis is a type of homogenous catalysis where the product of the reaction acts as the catalyst for the same reaction
• Why does the rate of an autocatalysed reaction increase as the reaction proceeds?

  As the product (which is the catalyst) forms, it increases in concentration, which accelerates the reaction rate.
• Why is the uncatalysed reaction between MnO₄⁻ and C₂O₄²⁻ very slow?

  Both MnO₄⁻ and C₂O₄²⁻ are negatively charged ions, which repel each other, resulting in a high activation energy.
• Which product acts as the catalyst in the reaction between MnO₄⁻ and C₂O₄²⁻?

  Mn²⁺ acts as the catalyst.
• Write the overall equation for the reaction between MnO₄⁻ and C₂O₄²⁻.

  1.2MnO₄⁻(aq) + 16H⁺(aq) + 5C₂O₄²⁻(aq) → 2Mn²⁺(aq) + 8H₂O(l) + 10CO₂(g)
• What happens to MnO₄⁻ in the first catalytic step of the reaction?

  MnO₄⁻ is reduced to Mn³⁺.
• Write the equation for the reaction where Mn²⁺ catalyses the conversion of MnO₄⁻ to Mn³⁺.

  MnO₄⁻(aq) + 8H⁺(aq) + 4Mn²⁺(aq) → 5Mn³⁺(aq) + 4H₂O(l)
• What role does Mn³⁺ play in the second step of the catalytic cycle?

  Mn³⁺ reacts with C₂O₄²⁻ to regenerate Mn²⁺ and produce CO₂.
• Write the equation for the reaction where Mn³⁺ reacts with C₂O₄²⁻.

  2Mn³⁺(aq) + C₂O₄²⁻(aq) → 2Mn²⁺(aq) + 2CO₂(g)Mn²⁺ is regenerated at the end of the catalytic cycle, allowing it to catalyse further reactions.
• Explain why the reaction rate is initially slow in the autocatalysed reaction?

  At the start, the catalyst (Mn²⁺) is not present in sufficient quantities, so the reaction proceeds slowly.