Transition metals as catalystsAQA A-Level Chemistry: Flashcards
What these 14 flashcards ask
- What is a heterogeneous catalyst?
- What is a homogeneous catalyst?
- Why can transition metals act as catalysts?
- Why is a support medium used?
- Which catalyst is used in the Haber process?
- Which catalyst is used in the Contact process?
- Write the first step of the Contact process mechanism.
- Write the second step of the Contact process mechanism.
- What is catalyst poisoning?
- What is the cost implication of poisoning?
- Why is the uncatalysed S₂O₈²⁻ + I⁻ reaction slow?
- Write the two steps for Fe²⁺ catalysing S₂O₈²⁻ + 2I⁻.
- What is autocatalysis?
- Write the steps showing Mn²⁺ autocatalysis.
Exam questions on Transition metals as catalysts
- An ammonia plant makes ammonia by the Haber process. A gaseous mixture of nitrogen and hydrogen at 450 °C and 200 atm is passed over a bed of solid iron. The plant manager reports that, whenever the feed gas is contaminated with traces of sulfur compounds, the output of ammonia falls.Explain why catalyst poisoning has a cost implication for the plant.2 marks
- Sulfuric acid is manufactured by the Contact process. Sulfur dioxide and oxygen are passed at 450 °C over vanadium(V) oxide, V₂O₅, which is spread thinly on the surface of inert silica pellets. The reaction is: SO₂(g) + ½O₂(g) ⇌ SO₃(g).Write two equations to show how V₂O₅ acts as a catalyst in this reaction.2 marks
- In aqueous solution, iodide ions react with peroxodisulfate ions: S₂O₈²⁻(aq) + 2I⁻(aq) → 2SO₄²⁻(aq) + I₂(aq). A technician finds that the reaction is very slow when the two solutions are mixed, but speeds up greatly when a few drops of iron(II) sulfate solution are added.Explain, with reference to the ions involved, why the uncatalysed reaction is slow.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).