Annotation Meaning
Correct response
Incorrect response
Omission mark
Benefit of doubt given
Contradiction
Rounding error
Error in number of
... [Show More] significant figures
Error carried forward
Level 1
Level 2
Level 3
Benefit of doubt not given
Noted but no credit given
Ignore
Blank page
Abbreviations, annotations and conventions used in the detailed Mark Scheme (to include abbreviations and subject-specific
conventions).
Annotation Meaning
DO NOT ALLOW Answers which are not worthy of credit
IGNORE Statements which are irrelevant
ALLOW Answers that can be accepted
( ) Words which are not essential to gain credit
__ Underlined words must be present in answer to score a mark
ECF Error carried forward
AW Alternative wording
ORA Or reverse argument
H432/01 Mark Scheme November 2020
5
SECTION A
Question Answer Marks AO
element Guidance
1 D 1 2.7
2 B 1 1.2
3 B 1 2.2
4 C 1 2.2
5 A 1 1.1
6 A 1 2.2
7 D 1 1.1
8 D 1 2.6
9 B 1 2.6
10 C 1 1.2 ALLOW 2 in the answer box
11 D 1 2.2
12 C 1 2.6
13 B 1 1.1
14 D 1 1.2 ALLOW 1 in the answer box
15 C 1 1.1
Total 15
H432/01 Mark Scheme November 2020
SECTION B
Question Answer Marks AO
element Guidance
16 (a) (The mean/average mass) taking into account the
relative abundancies of the isotopes
1 1.1 ALLOW
sum of (isotopic mass × %abundance)
sum of (isotopic mass × abundance) / total
abundance
DO NOT ALLOW average mass of the isotopes
(i) 2+ –
Mg Br
–
Br
Mg with no (or 8) outer electrons
AND
2 × Br with ‘dot-and-cross’ outer octet
Correct charges
2
1.2
2.5
ALLOW 8 electrons in Mg2+ BUT ‘extra’ electron
in Br– must match symbol for electrons in Mg2+
IGNORE inner shells and circles
ALLOW 1 mark if both electron arrangements
and charges are correct but only one Br is
drawn.
ALLOW 2[Br–], 2[Br]
– (brackets not required)
(ii) FIRST CHECK THE ANSWER ON ANSWER LINE
If answer = 1.71 × 1022 award 3 marks
-------------------------------------------------------------------------
n(MgBr2) = 1.74
184.1 = 0.00945….. mol
Moles of ions = 0.00945…. × 3 = 0.0283…. mol
Number of ions = 0.0283... × 6.02 × 1023 = 1.71 × 1022
3SF required
3 2.2×3 ALLOW ECF
Calculator answer = 9.451385117 × 10–3
ALLOW ECF from incorrect moles of ions.
e.g. 0.00945
Common error
5.69 × 1021 no × 3 2 marks
x
x
H432/01 Mark Scheme November 2020
7
Question Answer Marks AO
element Guidance
(c)* Refer to marking instructions on page 5 of mark scheme for
guidance on marking this question.
Level 3 (5–6 marks)
Explains all three melting point values and conductivities in
terms of structure, bonding, particles and relative strengths of
the forces.
There is a well-developed line of reasoning which is clear and
logically structured. The information presented is relevant and
substantiated.
Level 2 (3–4 marks)
Attempts to explain all three melting point values and
conductivities in terms of the structure, bonding, particles of all
three substances, but explanations may be incomplete or may
contain only some correct statements or comparisons.
OR
Correctly explains two of the melting point values and
conductivities in terms of the structure, bonding, particles.
There is a line of reasoning presented with some structure.
The information presented is relevant and supported by some
evidence.
Level 1 (1–2 marks)
Identifies only some of the structures, forces and particles
AND
Attempts to explain the melting point values OR conductivities
in terms of the structure, bonding, particles
There is an attempt at a logical structure with a line of
reasoning. The information is in the most part relevant.
0 marks
No response or no response worthy of credit.
6 1.1×3
2.1×3
Indicative scientific points may include:
Structure and bonding
Magnesium
• Structure: giant lattice
• Metallic bonding
• Delocalised electrons
Bromine
• Structure: simple molecular
• induced dipole dipole forces (London forces)
• (Between) molecules
DO NOT ALLOW (between) atoms
Magnesium bromide
• Structure: giant lattice
• Ionic bonding
• (Between) oppositely charged ions
Comparison of bond strengths
• Metallic and ionic bonds are stronger than
London forces
OR Metallic and Ionic bonds need more energy to
break than London forces
Conductivity
• Magnesium: conducts due to delocalised
electrons can move/mobile.
IGNORE ‘Carry’ charge for movement
• Magnesium bromide: In solid IONS cannot move;
in solution IONS can move.
DO NOT ALLOW electrons.
• Bromine: Does not conduct as no mobile charge
carriers.
H432/01 Mark Scheme November 2020
8
Question Answer Marks AO
element Guidance
(d) (i) Mg2+(g) + 2Br(g) + 2e–
Mg(s) + Br2(l)
2 1.2× 2 State symbols required.
CARE: Liquid state symbol for Br2
(ii) FIRST CHECK THE ANSWER ON ANSWER LINE
If answer = –346.5 award 2 marks
-----------------------------------------------------------------
2∆H hyd =
– 525 – 186 – (2 x 112) – 148 – 736 – 1450 + (2 x -325)
+ 1926
OR
– 525 – 186 – 224 – 148 – 736 – 1450 + 650 + 1926
OR
= – 693
∆H hyd = –346.5 (kJ mol–1)
2 2.2×2 ALLOW -347 (kJ mol–1) for 2 marks.
ALLOW for 1 mark ONE error with sign OR use of 2:
–693 (not divided by 2 at the end)
346.5 (wrong sign on answer)
Common errors for 1 mark
–2272.5 (–1926 instead of 1926)
-1386 (2 x -693 instead of -693)
–996.5 (–650 instead of 650)
–509 (2 × 325 not used)
–290.5 (2 × 112 not used)
–198.5 (148 instead of –148)
–160.5 (186 instead of –186)
–122.5 (224 instead of –224)
178.5 (525 instead of –525)
389.5 (736 instead of –736)
1103.5 (1450 instead of –1450)
For other answers, check for a single transcription
error or calculation error which could merit 1 mark
DO NOT ALLOW any answer which involves two
errors
e.g. –453 (2 × 325 not used AND 2 x 112 not used)
H432/01 Mark Scheme November 2020
9
Question Answer Marks AO
element Guidance
(iii) Equation: Mg2+(g) + 2Br –(g) → MgBr2(s)
CHECK THE ANSWER ON ANSWER LINE
If answer = –2433 award 2 marks
-----------------------------------------------------------------
Lattice enthalpy =
∆hyH(Mg2+) + 2 × ∆hyH(Br–) – ∆solH(MgBr2) OR
-1926 + (2 x -346.5) – (-186)
OR
∆fH(MgBr2) – 2∆atH(Br) – ∆atH(Mg)
– 1st IE(Mg) – 2nd IE(Mg) – 2∆eaH(Br) OR
-525 – (2 x 112) – 148 – 736 – 1450 – (2 x -325)
Lattice enthalpy = –2433 kJ mol–1
3 1.2
2.2 x 2
State symbols required
For other answers, check for a single transcription
error or calculation error which could merit 1 mark
DO NOT ALLOW any answer which involves two
errors
ALLOW ECF from incorrect answer to d(ii) [Show Less]