Higher Chemistry
Question Paper 2016
Questions 2 and 5 - Commentary
Candidate 1 (Question 2)
Q2a(i)
The candidate was awarded 1 mark because they have correctly stated there will
be increasing nuclear charge going across the period.
Q2a(ii)
The candidate was awarded 2 marks because they have identified that sodium
loses an electron to form an ion, and that the ion has fewer energy shells. The
comment about nuclear charge is not correct, but is not treated as conflicting in
this case.
Q2b(i)
The candidate was awarded 0 marks because they have made no indication of
increased shielding or decreased nuclear attraction. The mention of distance
from nucleus on its own is not enough to award the mark.
Q2b(ii)
The candidate was awarded 1 mark because they have identified that for the
second ionisation energy, the electron is removed from a stable shell.
Q2c(i)
The candidate was awarded 0 marks because their value of 683 lies outwith the
acceptable range (between 720 and 770).
Q2c(ii)
The candidate was awarded 1 mark because they have correctly stated that the
greater the ionic radii, the lower the lattice enthalpy.
Candidate 2 (Question 2)
Q2a(i)
The candidate was awarded 0 marks because although they have stated that
'more protons are added', they have then gone on to discuss the ‘atoms charge’
(without specifying nuclear charge) which is incorrect.
Q2a(ii)
The candidate was awarded 0 marks because they have not stated that an
electron has been lost or that the ion has fewer electron shells.
Q2b(i)
The candidate was awarded 1 mark because they have stated that there is a
shielding effect and the 'electrons become less attracted to the protons'.
Q2b(ii)
The candidate was awarded 1 mark because they have correctly stated that the
'next electron…taken from a full electron shell' (1 mark). They have also indicated
that the single electron in the outermost shell is the most shielded. This could be
taken to mean that the second electron must be less shielded (1 mark).
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Higher Chemistry
Question Paper 2016
Questions 2 and 5 - Commentary
Q2c(i)
The candidate was awarded 0 marks because their value of 733 lies within
acceptable range (between 720 and 770). However, the candidate has provided
an incorrect unit of kJmol. This is the first time that the candidate has supplied an
incorrect unit, and hence no mark is awarded. If the candidate supplies an
incorrect unit later in the script, it would not be penalised a second time.
Q2c(ii)
The candidate was awarded 0 marks because they have written a statement
implying that ionic radius is a dependent variable.
Candidate 3 (Question 2)
Q2a(i)
The candidate was awarded 0 marks because they have indicated that it is the
electrons in the outer shell creating the stronger pull, rather than the nucleus.
Q2a(ii)
The candidate was awarded 1 mark because they have stated that the sodium
ion has less energy levels that the atom. No mention is made of the loss of an
electron.
Q2b(i)
The candidate was awarded 1 mark because they have correctly stated that 'the
electrons are less under the influence or pull from the nucleus'.
Q2b(ii)
The candidate was awarded 0 marks because they have made no mention of the
loss of the second electron from a full/inner/stable shell or that shielding
increases/nuclear charge decreases.
Q2c(i)
The candidate was awarded 0 marks because their value of 706 lies outwith
acceptable range (between 720 and 770).
Q2c(ii)
The candidate was awarded 1 mark because they have stated that the lattice
enthalpy decreases as the atomic radii increases. ‘Atomic’ is treated as a slip in
this case because ‘ionic radii’ was in the stem of the question.
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Higher Chemistry
Question Paper 2016
Questions 2 and 5 - Commentary
Candidate 4 (Question 2)
Q2a(i)
The candidate was awarded 1 mark because they have correctly identified that
'protons being added to the nucleus' results in 'a stronger nuclear charge which
pulls the electrons closer'. Either one of these would be sufficient to award the
mark.
Q2a(ii)
The candidate was awarded 0 marks because they have not stated that the atom
loses an electron (to form an ion) or that the number of electron shells is less in
the ion than the atom.
Q2b(i)
The candidate was awarded 0 marks because although they have mentioned
attraction, they have not stated that this is due to the nucleus/nuclear pull.
Shielding is not mentioned.
Q2b(ii)
The candidate was awarded 2 marks because they have correctly stated that the
second electron is removed from a level closer to the nucleus (1 mark) and that
there is a 'stronger nuclear attraction to the next level' (1 mark).
Q2c(i)
The candidate was awarded 0 marks because their value of 697 lies outwith
acceptable range (between 720 and 770).
Q2c(ii)
The candidate was awarded 1 mark because they have given a correct statement
‘as the ionic radii increases, the lattice enthalpy decreases’.
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Higher Chemistry
Question Paper 2016
Questions 2 and 5 - Commentary
Candidate 1 (Question 5c)
5c(i)
The candidate was awarded 1 mark because they have correctly identified that
olive oil will use ‘more bromine’. Colour change at end point is the wrong way
round so the second mark cannot be awarded.
5c(ii)
The candidate was awarded 0 marks because they have made no mention of
polarity of molecules in their answer.
5c(iii)
The candidate was awarded 1 mark because they have stated that coconut oil
has more 'LDF forces to break'. There is no correct mention made of structure or
packing so the second mark cannot be awarded.
Candidate 2 (Question 5c)
5c(i)
The candidate was awarded 0 marks because they have not correctly identified
the colour change at the end point. The attempt to link degree of unsaturation to
speed of reaction is incorrect.
5c(ii)
The candidate was awarded 0 marks because the candidate's answer does not
relate to the question asked.
5c(iii)
The candidate was awarded 1 mark because they have correctly stated that ‘it
has more’ LDF. The use of the word ‘it’ is taken as coconut oil as this is first oil
mentioned in the question (1 mark). There is no correct statement made
concerning structure.
Candidate 3 (Question 5c)
5c(i)
The candidate was awarded 0 marks because they have stated that 'if the
bromine decolourises more'. It is unclear if this relates to volume of bromine.
Colour change is stated the wrong way round.
5c(ii)
The candidate was awarded 1 mark because they have correctly stated that
water is polar.
5c(iii)
The candidate was awarded 0 marks because they do not correctly describe the
structure of coconut oil. No mention is made of intermolecular forces.
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Higher Chemistry
Question Paper 2016
Questions 2 and 5 - Commentary
Candidate 4 (Question 5c)
5c(i)
The candidate was awarded 0 marks because they have made no mention of
adding bromine until the colour remains. The attempt to link degree of
unsaturation to speed of decolourisation is incorrect.
5c(ii)
The candidate was awarded 0 marks because they have given an explanation for
bromine, rather than oil.
5c(iii)
The candidate was awarded 2 marks because they have correctly stated that
coconut oil molecules are packed closer together (1 mark) and that there is
stronger intermolecular bonding (1 mark).
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