Advanced Level Chemistry Examination Paper Review 2009



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Advanced Level Chemistry Examination Paper Review 2009

  • Question 09 (Essay question)

Essay Question (2009 AL Chem)

  • 9. Write an essay to compare the chemistry of the s-block elements with that of the d-block elements.
  • A: Introduction/Definition (Max:1) B: Physical properties (Max:2) C: Chemical reactions (Max:3) D: Oxidation states (Max:2)
  • E: Complex formation (Max:3)
  • F: Catalytic activity (Max:3)

Marking of Essay question

  • Chemical knowledge : 10%
  • - Maximum mark for C.K. is 10 even when the sum of 6 areas > 10
  • Organization + Presentation : 10%
  • - O+PC.K.; O+P = C.K. – 0, -1, -2 but rarely -3 - Deduct marks for no sub-headings, no
  • paragraphing, poor English & organization
  • - Deduct marks for irrelevant or incorrect
  • materials

Example of marking

  • A 1
  • B 3  2
  • C 3
  • D 1
  • E 2
  • F 3
  • C.K. = 12  10
  • O + P = 09 (deduct 1 mark for P)
  • Total = 19

Observation-Overall

  • 1. Insufficient analysis and planning before writing
  • Imbalance of the coverage
  • Some put nearly equal weightings on similarities and differences (weighting on differences should be higher)
  • Some only list facts but unable to compare s- and d-
  • 2. Student only remember facts, but do not demonstrate understanding and apply it in different contexts
  • A lot of irrelevant or excess materials
  • Incorrect definition for d-block / confused with transition elements
  • Misuse of ‘low lying vacant orbitals’ to explain all characteristics of d-block elements

Observation-Area A

Observation-Area B

  • Spend too much time in this section
  • Give a lot of excess materials
  • Melting points, boiling points and hardness better answered.
  • List group trend of s- block & period trend of d-block, particularly atomic radius and IE. Correct explanations but no comparison  ZERO marks
  • List similar physical properties, e.g. they are metals, can conduct electricity, have higher density than non-metals  ZERO marks

Observation-Area B

  • Misconception:
  • all s-block metals have open structures
  • all d-block metals are close packed
  • colour of flame test and colour of complexes have same origins
  • ‘nuclear charge’ & ‘effective nuclear charge’ are the same
  • do not understand ‘d-d transition’- interaction between d orbitals and lone pairs of ligands to cause splitting of d orbitals into 2 energy levels.

Observation-Area C

Observation-Area D

  • can point out fixed O.S. in s-block and variable O.S. in d-block, but forget to give examples
  • explanation is not satisfactory. Many mention that d-block elements use low lying vacant d orbitals / extend the octet (since they do not have the concepts of hybridization)- confusion with NH3 VS PH3

Observation-Area E

  • Best performance among all areas. Many score 2 marks or more
  • Mistakes include ‘incorrect electric charges of the examples’, ‘misunderstanding between polarizing power and charge density’

Observation-Area F

  • Usually score 1 – 2 marks
  • Some mismatch between explanation and the type of catalyst
  • Common misspelling: ‘Habour process’ , ‘Harbour’, ‘absorb’, ‘absorbtion’, adsorbtion’
  • Incorrect equation: 2 Fe2+ + 2 I-  I2 + 2 Fe3+

Distribution of Marks for Q9 Paper 1C AL Chem 2009 Sample size: 328 papers

  • Marks
  • Frequency
  • 0
  • 6
  • 1
  • 12
  • 2
  • 13
  • 3
  • 12
  • 4
  • 10
  • 5
  • 17
  • 6
  • 17
  • 7
  • 24
  • 8
  • 21
  • 9
  • 17
  • 10
  • 24
  • 11
  • 19
  • 12
  • 21
  • 13
  • 22
  • 14
  • 24
  • 15
  • 18
  • 16
  • 14
  • 17
  • 12
  • 18
  • 7
  • 19
  • 6
  • 20
  • 12
  • 328


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