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Page 1

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1. (a) 25.4(%)
2
correct answer with or without working
accept 25(%)
accept 25.433....(%)
allow 26(%) for 1 mark
if incorrect answer 1 mark for identification of 44 as Mr of
useful product
or 173 as total Mr of reactants / products

(b) ignore references to energy / cheaper /…

Page 2

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Y ì2. (a) Pb Cl C O
76 13 2.2 8.8 1
207 35.5 12 16
1 mark for dividing one mass by Ar
allow upside down ratio to lose this mark only
= 0.367 = 0.366 = 0.183 = 0.55 1
1 mark for one correct proportion ­ accept…

Page 3

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3. (a) (i)
layers / lattice / giant structure / regular
1
pattern of atoms (diagram)
allow layers / lattice / giant structure
/ regular pattern of ions
do not accept particles
outer (shell) electrons 1
accept valence electrons
(free to) move (through whole structure) 1
accept delocalised / mobile…

Page 4

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4. (a)
2 marks for comments related to temperature
low / lower / lowest temperature (or 100 °C from graph) 1
ignore reference to catalyst
any one from: 1
(forward) reaction exothermic
if the temperature is increased the yield of product will
decrease or reaction right to left
2 marks…

Page 5

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(ii) sensible comment related to conservation of energy 1
eg cost of energy pollution aspects of burning fuels to
provide energy etc.
sensible comment related to conservation of materials 1
eg cost of materials
cost of converting raw materials into nitrogen and
hydrogen
natural gas is nonrenewable source
[10]


5.…

Page 6

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(ii) 1
or





ignore inner shell electrons of silicon
allow correct drawings without symbols
must clearly indicate four shared pairs of electrons with one
electron from each atom

(iii) Si H

1
= 0.05 = 0.15 1
1 3 1
for whole number ratio can be implied
Si H3 1…

Page 7

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(iv) C 1
accept c
(c) any four from: 4
giant structure / macromolecule / lattice / giant molecule
allow giant molecular / giant atomic structure
each silicon atom joined to four other atoms
(or diagram)
covalent bonds
bonds are strong or large amount of energy needed to break bonds…

Page 8

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(b) (i) (bonds broken =) 2005 (kJ)
1
(bonds formed =) 2046 (kJ) 1
energy change =
2005 ­ 2046 = (­)41 1
for correct subtraction ignore sign

(ii) (exothermic)
if in part (b)(i) answer is not 41
answer is consequential on endothermic or exothermic
shown
accept correct reasoning for…

Page 9

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(b) AlX3 1
for 1 mark





Harrow High School 9

Page 10

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(c) 7 / halogens 1
for 1 mark
[3]


9. (a) OH­ + H+
1
cancel 1 mark if equation is balanced incorrectly
H2O 1
award 1 mark only if Na+ and Cl­
included in the balanced equation

(b) (i) 27.5°C
1
answer must have the unit

(ii) neutralisation complete/greatest…

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