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This question is about catalysis - AQA - A-Level Chemistry - Question 5 - 2022 - Paper 3
Question 5
This question is about catalysis. Zeolites are used as heterogeneous catalysts in the catalytic cracking of alkanes. Tetradecane (C₁₄H₃₄) can be cracked to form oc... show full transcript
Worked Solution & Example Answer:This question is about catalysis - AQA - A-Level Chemistry - Question 5 - 2022 - Paper 3
Step 1
Step 3
Step 4
Explain, using equations where appropriate, why the reaction is slow at first and then goes quickly.
Answer
Initially, the concentration of the reactants is high, but there is not enough autocatalyst present to facilitate the reaction efficiently. As the reaction proceeds, the product (which serves as the autocatalyst) accumulates, leading to an increase in the reaction rate.
The overall reaction shows that as MnO₄⁻ is reduced by C₂O₂²⁻, the products generated can accelerate the breakdown of further reactants.
Step 5
Use the electrode potential data to suggest how Co²⁺ catalyses the reaction.
Answer
The electrode potential for Co²⁺ is lower than that for S₂O₈²⁻. This suggests that Co²⁺ can provide an alternative pathway with lower activation energy for the reaction to occur. The presence of Co²⁺ will facilitate the transfer of electrons, thereby increasing the rate of reaction between S₂O₈²⁻ and I⁻.