Catalytic Cycles: Tracing Steps Around a Closed Loop · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Walking around a catalytic loop

Science · Chemistry · ages 21-22
Name ______________________   Date ____________

  1. Why does the metal complex never show up in the overall equation?

    • It dissolves into the solvent
    • It is consumed and then regenerated
    • It never bonds to anything

  2. What is an elementary step?

    • One small step within a mechanism
    • The overall balanced equation
    • The moment the loop closes

  3. The slowest step of a cycle sets the pace of the whole reaction.

    Circle one:   True   False

  4. At each intermediate around the loop, what do you check?

    • Colour and smell
    • Mass and volume
    • Electron count and oxidation state

  5. You add up every step of a proposed cycle. What must the result show?

    • The intermediates cancel and the sum matches the overall equation
    • Every intermediate appears in the final sum
    • All oxidation states read zero

  6. The turnover-limiting step is too slow. What would raise the rate?

    • Cooling the mixture right down
    • Changing the ligands or warming the mixture
    • Removing the metal complex

  7. Two ligand sets on the same cycle give different major products. What does that show?

    • The solvent ran the reaction
    • The slow step stopped mattering
    • Ligand choice steers which product path wins

  8. A proposed cycle sums to an equation with a leftover metal species. What is wrong?

    • An intermediate failed to cancel, so the loop never closes
    • The rate law was measured badly
    • The ligands were poorly chosen
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Walking around a catalytic loop W1-mt_FmsXXdFRNC-s1

  1. It is consumed and then regenerated · What is made and then used up cancels out, so the loop closes back on its start.
  2. One small step within a mechanism · A mechanism is a list of small steps, and each entry is one elementary step.
  3. True · The loop can only run as fast as its narrowest doorway allows.
  4. Electron count and oxidation state · Sensible counts at every stop keep the proposed loop honest.
  5. The intermediates cancel and the sum matches the overall equation · Cancellation plus a matching sum is the test a real cycle must pass.
  6. Changing the ligands or warming the mixture · Help the slow step directly, and the whole loop runs faster.
  7. Ligand choice steers which product path wins · Ligands tilt the key step, so selectivity follows the ligand.
  8. An intermediate failed to cancel, so the loop never closes · A leftover species means the loop does not return to its start.
Worksheet · LightMySky