Chem paper 1 2021 mistakes

factors affecting the efficiency and lifetime of the heterogenous catalyst

Surface area, catalyst poisoning if the active site becomes blocked

how does iron act as heterogenous catalyst

reactants adsorbed onto surface of catalyst

Bonds break and new bonds formed

Products desorbed from catalyst

S2O82–(aq) + 2 I–(aq) → 2 SO42–(aq) + I2(aq)

Explain why this reaction is slow before the catalyst is added.

Two negative ions repel each other so the activation energy is high

equations to show how fe catalyses the reaction between peroxodisulfate ions and iodide ions in aqueous solution

S2O82- + 2fe2+ → 2SO42- + 2Fe3+

2Fe3+ + 2I- → 2Fe2+ + I2

Why do zinc ions not catalyse the reaction between iodide ions and the peroxodisulfate ions

It only has 1 oxidation state

Explain why an aqueous solution containing [Fe(H2O)6]3+ ions has a lower pH than an aqueous solution containing [Fe(H2O)6]2+ ions.

Fe3+ has a higher charge density than fe2+

Fe3+ more polarising

O-H bond in water ligands weakens and is more likely to release H+

Explain why [H2O] is not shown in the Kw expression.

It’s constant

Explain why the volume of sodium hydroxide solution added between each

pH measurement is smaller as the end point of the titration is approached.

To avoid missing the end point

Suggest why the two cobalt(III) complex ions in Table 8 have different electrode

potentials.

Different ligands