A-LevelChemistryChemical periodicity9701/41 · May/June 2020 · Q105 Marks
The electronic configuration of transition element Q is [Ar] 3d² 4s². Predict the likely oxidation states of element Q in compounds.
- (a)The electronic configuration of transition element Q is [Ar] 3d² 4s². Predict the likely oxidation states of element Q in compounds.[1]
- (b)Suggest why transition elements often show variable oxidation states in their compounds, but typical s-block elements such as calcium do not.[1]
- (c)Many enzymes contain transition element complexes. Describe, with the aid of a suitably labelled diagram, how an enzyme catalyses the breakdown of a substrate molecule. [Figure showing enzyme, substrate, active site, ES complex, enzyme + products][3]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [1] +4 and any of +1, +2, +3
- [1] close similarity of energy of the 4s and 3d sub-shells
- [3] diagrams
- [3] M1 (can be in words or diagram) substrate shape is complementary to active site
- [3] M2 (can be in words or diagram) the substrate bind / bonds / fits into the active site
- [3] M3 (can be in words or diagram) products are released
- [3] M4 (words) lower EA / bonds weakened (in substrate) Any three points
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