Higher Chemistry
Question Paper 2015 - Questions 1, 6, 8 & 12
Commentary
Question 1 b (ii)
Candidate 1
The candidate was awarded 0 marks because the answer focuses on the
electrons increasing but does not describe the increased nuclear charge.
Candidate 2
The candidate was awarded 1 mark because they correctly described the
increased nuclear pull on the electrons.
Candidate 3
The candidate was awarded 0 marks because there is no explanation given for
the decrease in the covalent radius.
Candidate 4
The candidate was awarded 0 marks because they have incorrectly implied that
the increased attraction between the nucleus and the electrons is due to the
increased number of electrons.
Question 1b(iii)
Candidate 1
The candidate was awarded 1 mark because they have correctly identified that
the intermolecular forces in sulfur are stronger than in phosphorus.
Candidate 2
The candidate was awarded 3 marks because they have correctly identified that
the LDFs in sulfur are stronger than those in phosphorus and they have correctly
identified the structure of both elements.
Candidate 3
The candidate was awarded 2 marks because the phrase - stronger London
dispersion forces – is taken to imply that both elements have LDFs and those in
the sulphur are stronger - although there is some confusion in their answer
(electronegativity ) LDFs were the only bond types mentioned .
Candidate 4
The candidate was awarded 2 marks because they have appreciated that both
elements have LDFs as intermolecular forces and they have stated that those in
sulfur are stronger however they have not appreciated that this is due to their
differing molecular structures.
2
Higher Chemistry
Question Paper 2015 - Questions 1, 6, 8 & 12
Commentary
Question 6a
Candidate 1
The candidate was awarded 0 marks because they have incorrectly described
this in terms of double bonds breaking.
Candidate 2
The candidate was awarded 0 marks because they have correctly identified that
bonds break but they have failed to name these as the hydrogen bonds.
Candidate 3
The candidate was awarded 1 mark because their four word answer is correct.
Candidate 4
The candidate was awarded 0 marks because they have no mention of hydrogen
bonds breaking.
Question 8b
Candidate 1
The candidate was awarded 1 mark because they have described how the
increase in the sodium ion concentration moves the equilibrium to the right.
Candidate 2
The candidate was awarded 0 marks because they have not described the effect
on the rate of the forward reaction and their explanation of the equilibrium shift
also includes the chloride ions.
Candidate 3
The candidate was awarded 0 marks because there is no mention of rate and
their answer describes an equilibrium shift in the wrong direction.
Candidate 4
The candidate was awarded 1 mark because they have no mention of rate
change but have correctly described the effect on the equilibrium in terms of the
sodium ions.
3
Higher Chemistry
Question Paper 2015 - Questions 1, 6, 8 & 12
Commentary
Question 12(c)(i)
Candidate 1
The candidate was awarded 2 marks because they have accurately stated that
ammonia is polar and trichloramine is non-polar and they have correctly
explained that in terms of electronegativities.
Candidate 2
The candidate was awarded 1 mark because they have correctly identified that
the bonds within ammonia are polar while those within trichloramine or not however they have not overtly commented on the overall polarity of the two
molecules.
Candidate 3
The candidate was awarded 2 marks because their answer has discussed the
electronegativity differences in both molecules and they have overtly stated that
trichloramine is a non-polar molecule and ammonia is a polar molecule.
Candidate 4
The candidate was awarded 1 mark because they have not fully described the
polarity of bonds in both molecules but they have stated that trichloramine is a
non-polar molecule and the use of the word whereas is deemed to imply that the
initial part of their answer is a comment on the polarity of the ammonia molecule.
4