Download Chemistry 2 Higher revision mark scheme

Page 1
M1.
(a)
oxygen / O2
(do not allow air) for 1 mark
1
(b)
(i)
idea that
it is a catalyst / it increases the rate of reaction / lowers
activation energy
for 1 mark
1
(ii)
the reaction is exothermic or releases energy / heat
for 1 mark
1
(c)
idea that
•
hot gases from the first reaction vessel need to be cooled
•
incoming gases / ammonia / oxygen need to be heated
•
there is an energy saving / cost saving
any two for 1 mark each
2
(d)
water and oxygen
(need both)
(accept H2O and O2)
for 1 mark
1
(e)
idea that
•
breaking bonds / breaking up molecules requires a lot of
energy / reaction has a high activation energy
•
gives a better / faster rate of reaction
•
the reaction is endothermic / more energy needed to
break existing bonds than to form new ones
allow a higher temperature gives a greater yield / pushes
the equilibrium position to the right
any two for 1 mark each
2
Page 2
(f)
ammonia (solution) / ammonium hydroxide
(credit NH3
NH4OH)
nitric acid / HNO3
in any order for 1 mark each
2
[10]
M2.
(a)
•
idea that
copper has free electrons / electrons that move
throughout the structure
gains 1 mark
but
•
in copper, electrons from the highest (occupied) energy
level /outer shell, are
free / can move throughout the structure
gains 2 marks
2
(b)
idea that
•
in graphite, only three bonds are formed by each carbon atom
for 1 mark
•
one outer electron (per atom), free to move
for 1 mark
•
an electric current is a flow of (free) electrons*
for 1 mark
(* this mark to be given in either (a) or (b) but not in both)
3
[5]
M3.
(a)
(i)
idea that
•
two hydrogen atoms share one pair of electrons
•
linked by a covalent bond
Page 3
•
each then has two outer electrons / a full outer shell / two
•
electrons in the highest (occupied) energy level
(2 marks may be awarded for a correct electron diagram i.e. with electrons on
boundary of or within marked area).
any two for 1 mark each
2
(ii)
idea that
•
helium atoms do not give / take / share electrons / react
•
because the (outer) shell / orbit is full
or
•
highest (occupied) energy level is full
(but not just “contains two electrons”)
for 1 mark each
2
(b)
idea that
•
the (attractive) forces between molecules are weak
(not bonds between atoms)
•
so little energy is required / it is easy for molecules to escape from the liquid*
/ escape from other molecules*
(allow evaporate / change into a gas)
for 1 mark each
2
[6]
M4.
(a)
2Cl– – 2e– → Cl2
(allow unaltered LHS to produce ½ Cl2)
+
Na + e– → Na
(allow × 2 for all terms)
(credit candidates who point out that hydrogen / H2 is in fact produced)
for 1 mark each
2
Page 4
(b)
for product 1*, idea of a solid / precipitate or silver bromide
gains 1 mark
but solid / a precipitate of silver bromide
gains 2 marks
for product 2*, idea of aqueous / a solution / dissolved (in water) / or sodium nitrate
gains 1 mark
(do not allow liquid)
but aqueous / a solution / dissolved (in water) of sodium nitrate
(*do not credit formulae)
gains 2 marks
4
[6]
M5.
(a)
Mg S O4
24 + 32 + 16 (×4) or 64 / evidence of all Ar’s
gains 1 mark
but (Mr) = 120
gains 2 marks
2
(b)
evidence that 24(g) magnesium would produce 120(g) mapesiurn sulphate
gains 1 mark
or correct scaling by 1/6
but 20(g) magnesium sulphate
gains 2 marks
[credit error carried forward from (a) with full marks in (b)]
2
[4]
M6.
(a)
2 Na + Cl2 → 2 NaCl
allow 2 Na+ Cl– for 1 mark
(allow Na + ½Cl2 → Na Cl)
1
Page 5
(b)
(i)
idea that
•
it has strong (attractive) forces/bonds between ions / charged
particles
for 1 mark
(not ‘..it has a rigid structure’- this defines a solid or ‘...particles
close together’ – they are in a liquid)
1
(ii)
ideas that
•
there is increased vibration of ions / particles on heating
•
ions have sufficient energy to overcome attractive forces / to
break out of the
•
rigid structure / to move about
(must be in terms of increased energy of particles lions)
each for 1 mark
2
(iii)
•
ions can go to electrodes / ions are free to move
for 1 mark
[do not credit ‘ions carry charges’]
1
(c)
ideas that
•
it has stronger attractive forces between atoms/particles (not ‘ions’)
•
each carbon atom forms covalent bonds with neighbouring atoms
each for 1 mark
2
[7]
##
(a)
idea that
some of the outer electrons of the atoms are free to move
can move anywhere across the (giant) structure
the flow of electricity is a stream of electrons
Page 6
each for 1 mark
or electrons carry a (negative electrical) charge
3
(b)
metal element
[shiny] appearance
[high] melting point
forms an oxide that reacts with acids to make a salt
1 of these for 1 mark
non metal element
forms an oxide that reacts with alkalis
with chlorine forms a molecular chloride
1 of these for 1 mark
semi-conductor suggests in between
this, or any other for 1further mark
[NB Maximum of 2 for arguing metal/non-metal only]
Under each head
1 wrong reason → maximum of 1 available
2 wrong reasons → no mark available]
3
[6]
M8.
(a)
(i)
2 H2 + O2 → 2 H2O (allow H2 + ½O2 → H2O)
both circled for 1 mark
1
(ii)
4 A1 + 3 O2 → 2 A12O3
all circled for 1 mark
1
(b)
idea that:
must end up with the same number of atoms
otherwise matter is shown to be lost/gained
doesn’t show correct amount of each element/compared
each for 1 mark
2
Page 7
(c)
idea that:
oxygen has 2 electrons short in outer shell ) in words or
chlorine has 1 electron short in outer shell ) indicated on diagram
(shared pair/covalent bond with) hydrogen
atom supplies one further electron*
*(but do not allow hydrogen gives away electron or ionic bond)
for 1 mark each
3
[7]
M9.
(a)
reference to
hydrogen (atoms)
)
nitrogen (atoms)
)
each for 1 mark
but not molecules
ratio of 1N to 3H atoms
for 1 further mark
or 1 nitrogen atom and 3 hydrogen atoms
(ignore any incorrect statements about nature of bonding)
3
(b)
evidence of
H=1
N = 14
O = 16
gains 1 mark
but
H=1
N = 14
O = 16 × 3 or 48
gains 2 marks
but 63
gains 3 marks
3
[6]
M10.
(a)
correct representation of 1 atom of hydrogen e.g.
Page 8
gains 1 mark
but correct representation of 1 molecule of hydrogen e.g. or H-H
gains 2 marks
2
(b)
idea that:
hydrogen/metals form positive ions/lose electrons
gains 1 mark
but hydrogen and the metals form positive ions/lose electrons
gains 2 marks
hydrogen/non-metals form covalent bonds/share electrons
gains 1 mark
but hydrogen and the non-metals form covalent bonds/share electrons
gains 2 marks
4
[6]
M11.
(i)
carbon dioxide (allow CO2)
for 1 mark
1
(ii)
sodium nitrate (accept correct formula)
for 1 mark
1
[2]
##
Page 9
(a)
Idea that
the electrons do not belong to specific atoms/delocalised electrons
[credit if done on appropriate diagram]
metal atoms form positive ions
the attraction which exists between particles with opposite charges, holds the metal
together
no specific bonds exist between adjacent atoms/ions
atoms/ions can slide over each other so allowing metals to bend
each for 1 mark
5
(b)
some electrons in the structure are delocalised/free to move
for 1 mark
these free electrons carry the electric current
for 1 mark
from left to right across the period, atoms of elements have
more free electrons
gains 1 mark
but from left to right across the period, atoms of elements have more free
electrons because they have more electrons in the outer shells
gains 2 marks
4
[9]
##
(a)
covalent bonds
for 1 mark
1
(b)
any reference to shared electrons
gains 1 mark
but idea that bond is shared pair of electrons
gains 2 marks
2
[3]
Page 10
M14.
(a)
any one from
(as a) catalyst
or to mix with promoters
to speed up the reaction (process)
or process is quicker do not credit just it is quicker
to save energy
to reduce costs
or process is cheaper
do not credit just it is cheaper
larger surface area
(than lumps of iron)
or larger surface area for the
(catalysed) reaction (to take place)
1
(b)
(i)
water or steam
and methane
or natural gas
or North Sea gas
both required either order
1
(ii)
EITHER
more (chance) of them colliding / coming into contact
do not credit just faster
OR volume of the product / ammonia less than / only half the
volume of the reactants / the nitrogen and hydrogen
1
(iii)
EITHER
680 (tonnes)
OR 28 (of nitrogen) → 34 (of ammonia)
accept any correct 14 : 17 ratio
1
560 (of nitrogen) → 34 × 20 (of ammonia)
3
[6]
Page 11
M15.
(i)
hydrogen, hydroxide and sulphate
all three and no others
any order
do not credit any formula(e)
1
(ii)
the anode is positive
1
(so) only the negative ions are attracted to it
or (so) only the hydroxide ions and the sulphate ions are
attracted (to it)
or (so) only the anions are attracted (to it)
1
(iii)
2H2O + O2 + 4e–
1
[4]
M16.
(a)
(i)
sodium........ positive or +
both required
1
chloride... negative or –
both required
do not credit chlorine
1
(ii)
ions not free (to move) in solid crystal / lattice
ions are free to move when sodium chloride is molten
1
or ions are mobile
do not credit when ions are molten
allow 'particles' for ions (1) mark
do not credit electrons etc
1
(iii)
dissolved in water
or in aqueous solution
accept in solution
accept in water
or when a gas/ vapour or solid it will not
Page 12
1
(b)
(i)
40
1
(ii)
(total) number of protons and neutrons (in the nucleus)
1
(c)
(i)
2Ca + O2 -+ 2CaO
accept any 2n : n : 2n ratio
do not credit if any other change has been made
1
(ii)
any two from
electron(s) is / are lost
from the outer shell / orbit / ring
or from the shell furthest the nucleus
or from the 4th shell
two / both (electrons are lost)
accept two electrons are lost for (2)marks
accept both electrons are lost from the
atom for (1) mark
2
[10]
M17.
(a)
CaCO3 + 2HC1 → CaC12 + CO2 + H2O
one mark for CO2 and H2O or H2CO3
one mark for balancing the equation
2
(b)
(i)
linear suitable scale for y axis
± one small square
1
accurate plots
deduct one mark for each error plot
1
smooth curve through the points or a line of best fit
this mark requires a neat smooth curve
1
Page 13
(ii)
curve becomes almost horizontal at or above 268.5
do not credit a straight line reaching 268.5 at 11 mins
accept a plot at 268.6
1
(iii)
steeper initial part to curve
1
becoming nearly horizontal between 268.6 and 268.4 g
1
[8]
M18.
(a)
Mg + 2H+ → Mg2+ + H2
* reactants correct in every detail
* products correct in every detail
if the spectator ions are sown then (1) mark should be
credited but only if they are shown correctly on both sides
e.g.
Mg + 2H+ + 2CI- → Mg2+ + 2CI- + H2
2
(b)
24 (parts) of magnesium → 2 (parts)
1
of hydrogen or equally clear working (so) 6 grams/g (are needed)
1
unit required
(c)
(i)
two (and no more) atoms shown to be sharing their single electrons
examples
do not credit if anything which contradicts the impression that
these are hydrogen atoms
1
Page 14
(ii)
(single) covalent (bond)
1
(d)
(×100) = 6 (just 6 is worth (1) mark)
1
× 100 = 6 or similar is (0)
do not credit 5.8823529 and the like
1
[8]
M19.
73 (seventy three)
if answer is incorrect allow 1 mark for the correct proportion
that H2:HCl is 1:2
and 1 mark for 36.5
[3]
M20.
(i)
1
Page 15
(ii)
weak forces
accept weak bonds
1
between molecules / intermolecular
reject intramolecular
1
[3]
M21.
(a)
(i)
2.25
correct answer gains three marks
if incorrect allow 1 mark for 2 correct
readings (130 and 175) and further mark for 45 ÷ 20
allow e.c.f.
3
(ii)
concentration of reactant(s) lower
1
fewer collisions per second / time unit
1
(b)
labour costs lower / enzymes costs lower
not stop and start
1
[6]
M22.
(a)
10.86
accept answers between 10.64 to 10.9
if answer is incorrect allow 1 mark for
rfm FeSO4 = 152
2 marks for 152 × 4/56
3
(b)
2 Fe + 3 H2SO4 → Fe2(SO4)3 + 3H2
accept other correct multiples for balancing
1
[4]
Page 16
M23.
(a)
Quality of written communication: All scientific words used correctly
(covalent, bonds, atoms)
1
any two from
•
large numbers of covalent bonds
allow giant lattice / structure
•
between atoms
do not accept between molecules
•
(covalent) bonds strong
accept need much energy to break
2
(b)
each carbon has 4 electrons
1
Page 17
one shared pair
1
four shared pairs
1
[6]
M24.
(a)
1400
1
(b)
980
correct answer gains full credit
160 tonnes Fe2O3 produces 112 tonnes Fe
if incorrect allow one mark for relative formula mass iron
oxide = 160
allow e.c.f.
1400 tonnes Fe2O3 will produce 1400 / 160 × 112 tonnes Fe
use of 2000 tonnes Fe2O3 – deduct one mark only if
working out is correct
4
[5]
M25.
(a)
X – (metal) atom / ion
1
Y – electron
1
(b)
free electrons or electrons move
1
(allow metal) atoms / ions to slide over each other
OR
bonding non - directional for 2 marks
Page 18
1
[4]
M26.
1000 × 1000 / 0.065
gains 1 mark
but
15384615g (accept answer rounded to minimum of 2 sig. figures)
(accept answer with no units or correct units but incorrect unit loses one mark)
(answer correctly worked out in kg is acceptable)
gains 2 marks
[2]
M27.
(a)
sodium hydroxide / caustic soda / NAOH
for 1 mark
1
(b)
negative ions move to the positive electrode etc.
/because it is negative
/opposite charges attract
for 1 mark
1
(c)
loss of electrons
for 1 mark
1
[3]
M28.
(i)
neutralise (the acid) / reduce acidity / because it is alkaline /increases pH
Page 19
for 1 mark
1
(ii)
CaO = 56
Ca(OH)2 = 74
each for 1 mark
2
(iii)
mass = 1000 × 74/56
gains 1 mark
= 1321 kg (1320 accepted)
gains 2 marks
(error carried forward from (ii))
56g → 74g
1 g → 74/5 6 g (1 mark)
2
[5]
M29.
(a)
made of layers
of carbon atoms
weak forces of attraction between layers (owtte) / weak
vertical bonds i.e.
candidate refers to the diagram
layers can slide over each other
layers peel off
each for 1 mark
(b)
because there are electrons
which are free (to move)
reason for free electrons / each carbon atom has 3 covalent bonds
each for 1 mark
to max 5
[5]
Page 20
M30.
56
74
each for 1 mark
[2]
M31.
(a)
some electrons from outer shells
(some electrons) free to move/mobile
through whole structure/between atoms/sea of electrons
hold atoms together
for 1 mark each
or positive ions in a sea of electrons (owtte)
2 marks
atoms in regular structure/layers
giant structure
close packed
credit diagrams – look for labels
for 1 mark each any 4
4
(b)
(i)
electrons,
free to move (reference to electrons)
for 1 mark each
2
(ii)
layers/atoms can slide over each other
for 1 mark
1
(iii)
free electrons hold atoms strongly together/strong forces of attraction/bonds
(between atoms)/tight packing of atoms
for 1 mark
1
[8]
##
(a)
(2) : (6) : (2)
Page 21
All 3 correct gains 2 marks
2 correct gains 1 mark
2
(b)
no water present/moist air cannot enter/do not thoroughly mix/
must be in solution etc.
for 1 mark
1
(c)
(i)
hydroxide (ion) / OH–
for 1 mark
1
(ii)
hydrogen (ion) / H+
for 1 mark
1
(iii)
water/H2O/hydrogen oxide
for 1 mark
1
[6]
M33.
(a)
Gas A = Chlorine / Cl2 not Cl and Gas B = Hydrogen / H2 not H
for 1 mark
Solution C = sodium hydroxide/NaOH/spent brine
for 1 mark
2
(b)
(i)
2, 2
for 1 mark
(ii)
2, 2
for 1 mark
2
(c)
water/H2O/hydrogen oxide not hydrogen hydroxide
for 1 mark
1
Page 22
(d)
ions/positive ions/negative ions/cations/anions
not charged particles/positive particles/negative particles
not H+ / Cl-/Na+ / OHAllow hydrogen ions etc.
not sulphate ions
for 1 mark
1
[6]
##
(a)
covalent/description of covalent
for 1 mark
1
(b)
forces/bonds between the molecules/particles (not atoms) are weak
for 1 mark each
2
(c)
non-flammable so it will not burn etc.
extremely unreactive so it will not react with materials in the transformer,
does not conduct electricity so it can insulate the transformer
gas so it has freedom to move and insulate whole area
for 1 mark each
3
[6]
##
(a)
potassium / K
for 1 mark
1
(b)
carbon dioxide / CO2
for 1 mark
1
(c)
losing
Page 23
electrons
gaining
electrons
for 1 mark each
4
(d)
(i)
power supply, (not mains)
beaker containing solution,
(inert) electrodes and circuit
ammeter or bulb/
(or see bubbling etc. at electrodes written by drawing)
for 1 mark each
4
(ii)
reading on ammeter/bulb lights / (solution) conducts (electricity)
bubbling / gas produced
hydrogen produced
chlorine / oxygen produced
ions move
to electrodes (must be linked to ions move)
negative ions move to the positive electrode
and/or positive ions move to the negative electrode
negative ions lose electrons
and/or positive ions gain electrons
any 3 for 1 mark each
3
[13]
M36.
(a)
C16 H34
for 1 mark
1
(b)
electron
gains 1 mark
but shared electrons
gains 2 marks
2
[3]
Page 24
M37.
(a)
4 HCl / 2H2O, allow multiples or fractions if whole equation balances
for 1 mark
1
(b)
germanium tetrachloride + water = germanium oxide + hydrochloric acid
If symbol equation given it must be correctly balanced
Allow germanium
for 1 mark
1
(c)
to purify the germanium oxide/remove impurities/give in
pure product/to make pure germanium
for 1 mark
1
ensure complete reaction/reaction does not give a good yield
not to increase efficiency/to purify germanium
for 1 mark
1
(d)
(i)
remove oxygen/addition of hydrogen/gain up electrons allow remove
oxygen molecules
(ii)
GeO2 = 73 + (2 × 16) = 105
mass of germanium = 525 × (73/105)
= 365 g
(or alternative methods)
apply consequential marking
for 1 mark each
3
(e)
(i)
germanium is shiny/lustrous
conducts a small amount of electricity *
germanium oxide reacts with hydrochloric acid
(and) metal oxides react with acid
metal oxides are basic
metal oxides are reduced by hydrogen
Information must be taken from the passage.
Page 25
Apply the list principle if more than three answers are given.
Assume the word ‘it’ refers to the metal.
any 3 for 1 mark each
3
(ii)
germanium is brittle
germanium tetrachloride is a (volatile) liquid
made of molecules
germanium tetrachloride has covalent bonding or when two non-metals
react they have covalent bonding
GaC14/the salt of germanium undergiven hydrolysis/reacts with water
germanium is not a good conductor of electricity*
* conductivity mark can only be given once
any 3 for 1 mark each
3
[13]
M38.
(a)
2, 8, 8, 1
for 1 mark
1
(b)
for 1 mark
Ignore symbol in middle but structure must be drawn NOT 2,7
If covalent; can score mark for changes but not for diagram
Arrow showing electron transfer from metal atom to non-metal atom = 2 marks
If the ions are not identified then cannot score mark for changes
Page 26
4
[5]
M39.
(a)
(i)
Na2CO3 or (Na+)2 CO32– must be completely correct
for 1 mark
1
(ii)
(1)
decomposition of limestone
or decomposition of coal
or decomposition of sodium hydrogen carbonate (owtte.)
allow equations even if not
correctly balanced
any 1 for 1 mark
1
(2)
breakdown/split up not decomposed by heat
for 1 mark each
2
(iii)
carbon dioxide or ammonia [CO2] or [NH3]
for 1 mark
1
(b)
(i)
zinc carbonate or zinc hydroxide
allow formulae if completely correct
for 1 mark
1
(ii)
(zinc carbonate) is insoluble (in water)
((i) and (ii) are independent marks)
for 1 mark
1
[7]
M40.
(a)
(i)
hydrogen/H2
for 1 mark
Page 27
1
(ii)
i.e. 2Cl¯ -2e– →Cl2
for 1 mark
1
(iii)
hydroxide or OH–
for 1 mark
1
(iv)
sodium hydroxide/caustic soda/NaOH/bleach/
chemical name of bleach
for 1 mark
1
(b)
(i)
Na2CO3 or (Na+)2 CO32–
for 1 mark
1
(ii)
coal
water/H2O
limestone/CaCO3/calcium carbonate
any one for 1 mark
1
(iii)
calcium chloride/CaCl2/sodium hydrogen
carbonate/NaHCO3
for 1 mark
1
(iv)
decomposition/heating of limesstone
decomposition/heating of coal
decomposition/heating of sodium
hydrogen carbonate
any 1 for 1 mark
1
described change e.g. NaHCO3 → Na2 CO3
(Use judgement)
breakdown (owtte.)
by heat
for 1 mark each
2
(v)
carbon dioxide/CO2 or ammonia/NH3
Page 28
for 1 mark
1
(c)
(i)
zinc carbonate/ZnCO3/zinc
hydroxide/Zn(OH)2
for 1 mark
1
(ii)
It is insoluble
zinc carbonate is insoluble in water
for 1 mark
1
[13]
M41.
(a)
8 marks
Particularly well structured answer with most points mentioned.
7-6 marks Well structured answer. The two metals will have been
compared rather than simply listing advantages/disadvantages. Most
of the advantages and disadvantages of each metal have been mentioned.
5-3 marks Some structure to the answer. An attempt to compare the metals
by giving some advantages and disadvantages.
2-1 marks Little structure or attempt to compare. Marks gained by listing a few
advantages or disadvantages.
Advantages of Nickel:
Relatively low cost which makes the sparking plugs cheaper to produce.
Quite high melting point which is needed because the temperature in the
engine is very high.
Good conductor of electricity needed to carry electricity into combustion
chamber to produce spark.
Page 29
Disadvantages of Nickel:
Subject to corrosion in engine which means they only last a short time
because nickel is higher in reactivity than platinum.
Idea that this leads to reduced efficiency, unburnt petrol and air pollution.
Advantages of Platinum:
Less susceptible to corrosion (not corroded) because platinum is very low in
reactivity.
Idea that this improves efficiency and reduces pollution.Higher melting point than nickel to withstand the high temperatures in the
combustion chamber.
Last a lot longer than nickel electrodes due to low reactivity.
(Sensible extension here could be longer service intervals etc.)Good conductor of electricity as for nickel.
Extension here could be linked to the idea that the conductivity
does not deteriorate as quickly as nickel.)
Disadvantages of Platinum:
Cost which will make the sparking plug more expensive.
A good candidate might justify cost by longer life, better fuel consumption and
less pollution.
8
(b)
(i)
giant structure/lattice/regular arrangements of atoms
any for 1 mark
of atoms/of ions (provided free electrons mentioned)
either for 1 mark
delocalised or free electrons
for 1 mark
3
(ii)
electrons free/can move
for 1 mark each
2
[13]
Page 30
M42.
(a)
(i)
H+ + OH- → H2 O/H3O+ + OH- → 2H2 O
for 1 mark
1
(ii)
1 point from e.g.
smaller bits
bigger surface area
faster reaction
dissolve faster
more particles open to attack by acid
any 1 for 1 mark
1
(iii)
MgCO3 or MG2+CO32- or CO3 Mg
for 1 mark
1
(b)
(i)
2 HCl
for 1 mark
1
(ii)
aqueous/dissolved in water (not in solution)
for 1 mark
1
(iii)
CO2/gas evolved/gas has mass
for 1 mark
1
(c)
(i)
plotting points
scales
curve
labelling axes including units
for 1 mark each
4
Page 31
(d)
faster
same final mass
for 1 mark each
2
[12]
M43.
(i)
neutralisation/acid base reaction
for 1 mark
1
(ii)
17 (tonnes)
give 80 (tonnes) (even if only in working)
for 1 mark each
320 (tonnes) or alternative method)
3 marks for correct answer
(if 17 and 80 not given allow 1 mark for correct answer using their figures)
3
[4]
M44.
(a)
(i)
45%
for 1 mark
1
(ii)
126 000 (consequential on (i))
for 1 mark
1
(b)
(i)
Cl2 = 71
1 × 71/24 or correct mathematical attempt
for 1 mark
(If Cl2 wrong take figure given)
for 1 mark
Page 32
= 2.96 kg
gains 3 marks
(or alternative methods)
(if units not given - 3 marks. If units wrong - 2 marks)
3
(ii)
any sensible eg. bleach/disinfectant/antiseptics/kill bacteria/
sterilise water/solvents/refrigerents/CFCs/PVC
(not water treatment or warfare)
for 1 mark
1
[6]
M45.
(i)
1
electrons
for 1 mark
(ii)
covalent
1
for 1 mark
(iii)
made of small molecules:
usually gas or liquid
) dependent on
have low melting points ) having first
have low boiling points ) point above
forces between molecules are weak
any 1 for 1 mark
3
[5]
M46.
(a)
40 + 12 + (3 × 16) = 100
each for 1 mark
2
Page 33
(b)
Mr of CaO = 56
for 1 mark
mass required = 60 × 100/56
for 2 marks
= 107.1
for 1 mark
4
(c)
(i)
calcium hydroxide
1
(ii)
solid
1
[8]
M47.
(a)
(i)
14 electrons =
gets 1 mark
2.8.4 =
gets 2 marks
2
(ii)
outer shell electrons
1
(iii)
same number of electrons in outer shell
1
(b)
(1)
shiny
conducts electricity
(2)
oxide neutralises alkalis
covalent bonds
4
[8]
M48.
(a)
any (must be named)
Page 34
1
(b)
F2
1
(c)
–/F–
1
(d)
(i)
covalent
1
(ii)
made of molecules etc.
type of bonding when non-metals react.
1
[5]
M49.
(a)
sodium
1
(b)
neutralisation
1
(c)
increase/inc. number
1
(d)
H+
1
(e)
OH–
(f)
H+ + OH– → H2O
1
[6]
M50.
(a)
electrolytes
1
(b)
oxidation
1
Page 35
electrons lost
1
(c)
2H+ + 2e– → H2
minus sign on e– not needed
2
(d)
concentration increases
1
OH– discharged from water / water decomposes
1
H+ concentration increases / H2 and O2 evolved
1
[8]
M51.
(a)
(i)
iron must be named
do not accept Fe
1
(ii)
hydrogen
1
and oxygen mixtures
1
burn rapidly
1
(b)
(i)
lowers concentration
accept dilutes the acid
do not accept cooling
1
less collisions (between particles)
1
(ii)
H+ (aq)
accept H3O+ only if 2 in front of H2O
Page 36
1
OH (aq)
if spectator ions correctly included on both sides, maximum =
1 mark
1
(iii)
Ca(OH2) weak alkali
accept NaOH strong alkali
1
Ca(OH)2 causes no problems
accept NaOH causes named problem
(eg caustic or exothermic or burns or corrosive)
1
[10]
M53.
144
accept TiCl4 = 190 for 1 mark
accept another correct step in calculation
eg 570/190 = 3 for 1 mark
[3]
M54.
(i)
same number of protons and electrons
accept equal numbers of protons and electrons
do not accept they are neutral
1
(ii)
same element
accept all atoms are potassium
1
same number of protons
accept same atomic number
accept they all have 19+
1
Page 37
different number of neutrons
accept different mass numbers
do not accept different atomic masses
1
[4]
M55.
(i)
can be from diagram chlorine (2.8).7.
accept chlorine needs one more electron
1
can be from diagram shares a pair of electrons
1
shared pair of electrons is a covalent bond
do not accept ionic bond
1
(ii)
can be from diagram and appropriately annotated sodium (2.8). 1.
and chlorine (2.8).7
1
sodium loses one electron and chlorine gains one electron
1
Na+ and Cl– formed
1
bond formed between oppositely charged ions or ionic bond is formed
do not accept covalent bond
1
[7]
M56.
(i)
a reaction in which the products can
be changed back to reactants
accept a reaction that can go forwards or backwards
1
Page 38
under certain conditions
1
(ii)
Mr CaCO3 = 100
1
Mr CaO = 56
1
mass of CaO = 140 (tonnes)
1
mark consequentially
[5]
M57.
(a)
(i)
test: limewater
accept calcium hydroxide solution
1
result: ‘goes’ cloudy
accept white or milky
do not accept misty or chalky test must be correct before
result mark can be considered
1
(ii)
2 NaHCO3 + H2SO4 →
Na2SO4 + (2) H2O + (2) CO2
1
correctly balanced
1
(b)
(i)
H+ + OH–
1
→ H2O
deduct one mark if incorrectly balanced
accept H3O+ instead of H+ then 2H2O needed for balance
1
Page 39
(ii)
pH increases
accept numerical indication
1
(c)
addition of sulphuric acid
1
correct use of an indicator
accept idea of forming a neutral solution
1
crystallisation (of neutral solution)
accept description using evaporation
1
[10]
M58.
(a)
calcium atom loses two electrons
accept diagrams with correct labelling
1
(each) fluorine atom gains one electron
accept two electrons transfer from a calcium atom to the two
fluorine atoms for these first two marks
1
forming full (outer) shells of electrons
accept forming full (outer) energy levels or noble gas
electronic structures
do not accept stable unless qualified
1
giving the ions Ca2+ and F
1
attraction between ions of opposite charges
accept electrostatic attraction between ions
if candidate mentions sharing or pairing of electrons then no
credit
if explanation is entirely correct but they state this is called
covalent bonding, the maximum mark is four
1
(b)
atoms of the same element
Page 40
1
atomic number is same
accept each contains 92 or same number of protons
1
mass numbers differ or each has a different number of neutrons
1
one has 146 neutrons the other has 143 neutrons
accept one has three more or less neutrons than the other
1
(c)
(i)
349
1
(ii)
349g UF2 produces 235g U [1]
first mark can be awarded if answer is incorrect
answer = 117.5
1
[12]
M59.
(i)
electrolysis
1
(ii)
oxidation
1
(iii)
hydroxide ions or OH–
accept sodium hydroxide or hydroxide or OH for one mark
only
2
(iv)
H+ + e–
1
H2
ignore any state symbols
1
2H+ + 2e– → H2
Page 41
accept H+ + e-→ H for one mark only
1
[7]
M60.
answers apply to:
accept diagrams and/or descriptions
carbon dioxide CO2
ammonia NH3
methane CH4
water H2O
*outer electronic structure of one atom correct or needs
correct number of electrons to complete outer shell
1
*outer electronic structure of other atom correct or needs
correct number of electrons to complete outer shell
1
*one shared pair of electrons (as one covalent bond)
use of ions or reference to ionic bonding negates this mark
1
*outer electronic structure of compound correct or each atom now
has a full outer shell/noble gas electron structure
1
[4]
M61.
352 g gains 3 marks
(moles C8H18 = 114 / 114 = 1 mole)
moles CO2 = 8 (1)
mass CO2 = 8 × 44 (1) = 352 g (1)
1 mark for each point
Page 42
(ecf allowed between parts)
or
114 → 8 (1) × 44
(1)
114 → 352 g
(1)
ecf allowed between parts
[3]
M62.
hydrogen ions (from acid) or protons / H+
1
react with hydroxide ions (from alkali) / OH
1
to produce water
H + OH
H2O gains all 3 marks
ignore state symbols
molecules of hydrogen ions and molecules of
hydroxide ions produce water = 2 marks
if they fail to get any of the above marks they can
get 1 mark for neutralisation / product neutral
1
[3]
M63.
(a)
Mr (SiO2) = 60
if Mr incorrect ecf for max 2
1
60 g SiO2 → 28 g Si
correct answer for 3 marks
1
2.14 g SiO2 → 1 g Si
allow 2, 2.1, 2.14 (or anything rounding to 2.14), 2.16 or 2.2
a unit is not required but an incorrect unit loses the third
mark
Page 43
OR Mr (SiO2) = 60 (1)
moles if silicon needed =
= 0.0357
mass of SiO2 needed = 0.0357 × 60 (1)
= 2.14 g (1)
allow 2, 2.1, 2.14 (or anything rounding to 2.14), 2.16 or 2.2
OR Mr (SiO2) = 60 (1)
mass SiO2 = 1 ×
(1)
= 2.14 g (1)
allow 2, 2.1, 2.4 (or anything rounding to 2.14), 2.16 or 2.2
3
(b)
(i)
MgO(s) + 2HCl(aq) → MgCl2(aq) + H2O(l)
penalise incorrect symbols correctly balanced equation for 1
mark state symbols for 1 mark
allow correct multiples / fractions
2
(ii)
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
Page 44
(iii)
Si
H
1
= 0.05
= 0.15
1
1
3
for whole number ratio can be implied
1
Si H3
accept H3 Si or any correct formula with 1:3 ratio
if in step 1 they get either of ratios incorrect they lose first 2
marks but can be ecf for 3rd and 4th mark
evidence of mass / Ar
1 mark
proportions of each
1 mark
whole number ratio
1 mark
correct formula
1 mark
1
(iv)
C
accept c
1
(c)
any four from:
•
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
accept hard to break bonds
•
large number of bonds to be broken
mention of giant ionic structure or intermolecular forces or
intermolecular bonds
max 1 mark
diamond or carbon discussion max 3 marks unless clearly
linked to silicon
4
[15]
Page 45
168g → 44g
M64.
1
1g →
1
11g → 2.88g (2.9g)
care with rounding
1
or
Mr values 84 and 44
(1)
moles hydrogen carb =
(1)
mass of CO2 =
= 2.9g
answer 2.88 to 2.9 gets 3 marks
answer of 3 gets 2 marks
(1)
[3]
M65.
(a)
(i)
Quality of Written Communication
The answer to this question requires ideas in good English in a sensible order
with correct use of scientific terms. Quality of written communication should be
considered in crediting points in the mark scheme.
maximum 2 marks if ideas not expressed well
layers / lattice / giant structure / regular pattern of atoms (diagram)
allow layers / lattice / giant structure / regular pattern of ions
do not accept particles
1
outer (shell) electrons
accept valence electrons
1
(free to) move (through whole structure)
accept delocalised / mobile / free
Page 46
1
(ii)
the free electrons (allow the metal to conduct electricity)
accept electrons move / mobile / delocalised
1
(iii)
atoms / ions / layers can slide / slip / move over each other
1
(b)
(i)
copper oxide formed or Cu reacts with oxygen or Cu is oxidised
1
this is a poor conductor or gets in the way of free moving electrons or fewer
mobile electrons
do not accept electricity
1
or
oxygen atoms / oxygen molecules / oxide ions in metal
do not accept oxygen pockets / bubbles
prevents / disrupts flow of electrons /
current or fewer mobile electrons (1)
do not accept macro explanations
do not accept electricity
(ii)
hydrogen reacts with oxygen or water is formed or hydrogen reduces
copper oxide etc.
1
[8]
M66.
(a)
H+(aq) + OH– (aq) → H2O(l) or
H3O+(aq) + OH–(aq) → H2O(l)
mark for correct equation
mark for state symbols
any other symbols = 0 marks
accept correct spectator ions e.g.
Na+(aq) + OH– (aq) + H+(aq) + Cl– (aq) → Na+(aq) + Cl– (aq)
Page 47
+ H2O(l)
2
(b)
(i)
nitric acid and ammonia (solution)
HNO3
NH3 / NH4OH
mark for both
accept ammonium hydroxide /
NH4OH instead of ammonia
do not accept ammonia hydroxide
do not accept hydrogen nitrate solution
accept correct formulae
1
(ii)
provides oxygen or oxidising (agent) or oxidant
do not accept it contains oxygen alone
or rich in oxygen
1
[4]
M67.
(a)
2.8.3 on diagram as Xs / dots
or e
accept paired or unpaired
1
(b)
any two from:
•
electrons in highest energy level or electrons in outer shell
•
electrons are delocalised or sea of electrons
•
electrons are free or electrons move around / flow
•
electrons carry charge / current
ignore carry electricity
2
[3]
Page 48
M68.
(a)
nanoparticles / they are small(er)
accept 1–100 nm or a few atoms in size
1
so can easily pass through pores / skin / cell / membranes / arteries / veins /
capillaries / into blood stream owtte
must be a comparative statement
can be inferred from smaller particles
allow absorbed for pass through
1
(b)
any one from:
•
may be toxic (to cells / specific cells)
allow may harm / damage / kill cells / organs / tissues or may
cause cancer
•
to ensure safety or reduce risk or risk of litigation
allow may cause allergies / side effects
ignore harmful / dangerous unqualified eg harmful to body /
people
•
nanoparticles may have different properties
•
to see if they pass into the body
1
(c)
any two sensible ideas from eg:
•
testing is expensive or testing costs money
allow it costs money
ignore litigation
•
testing is time consuming
•
don’t see any reason to test since normal sized particles (of titanium oxide) do
not cause harm
accept normal sun cream does not cause harm owtte
•
don’t want to risk not producing a popular product (owtte)
eg if unsafe will have to stop production or have to remove
product if toxic
•
testing process / unfavourable results might cause alarm / reduce sales /
reduce profit (less money)
•
do not want to be seen doing animal testing
Page 49
2
[5]
M69.
Pb
76
207
Cl
13
35.5
C
O
2.2
8.8
12
16
1 mark for dividing one mass by Ar
allow upside down ratio to lose this mark only
1
= 0.367
=
0.366
= 0.183
= 0.55
1 mark for one correct proportion – accept to one d.p. or
rounded up to 1 d.p.
1
1 mark for all four correct proportions correctly rounded
1
2
2
1
3
or Pb2Cl2CO3
1 mark for correctly written formula
or
correct whole number ratio
correct formula without working gets only 1 mark.
e.c.f. can be allowed from incorrect proportions to formula or
ratio
1
[4]
M70.
any four points from:
•
high melting point owtte
ignore boiling point
•
many or all atoms joined together
•
each silicon (atom) joined to four oxygen (atoms) or each oxygen joined to two
silicon
•
covalent (bonds)
Page 50
•
many bonds would need to be broken
•
strong bonds
allow hard to break bonds
•
lot of energy / heat needed to break bonds
allow high temperature needed to break bonds
•
giant / macromolecular / lattice / diamond structure
•
unreactive
allow doesn’t react with materials within furnace = 1 mark
•
rigid / hard structure
•
no free electrons
•
poor conductor of heat
giant covalent structure = 2 marks
max 3 if ionic / metallic bonding mentioned
ignore electrostatic
ignore molecules / intermolecular forces
[4]
M71.
(a)
Compound A
any one from:
accept correct formulae
•
sodium bromide
•
potassium bromide
•
ammonium bromide
•
hydrogen bromide
•
any metal bromide except silver and lead.
1
Compound B
silver nitrate
accept silver sulphate
1
(b)
the silver compound will decompose / silver ions be reduced to silver (owtte)
Page 51
accept film would darken owtte
accept any idea of light changing silver bromide / silver ions /
silver nitrate / silver sulphate
allow ‘forms a black solid’ / it would turn black
1
(c)
precipitation
accept descriptions of precipitation reactions
accept double decomposition
accept precipitate
do not allow displacement
1
(d)
electrons
1
are gained
the second mark must be linked to electrons
accept it / silver / silver ions gains electrons for both marks
ignore references to oxygen
1
[6]
M72.
(a)
2Mg + O2 → 2MgO
accept correct multiples / fractions
1
(b)
electrons do not need to be paired
accept dots / circles / e instead of crosses
Page 52
do not allow 2.6 without diagram
1
(c)
electrons do not need to be paired
allow without bracket s/ must have the charge
accept dots / circles / e instead of crosses
ignore extra empty outer shells
ignore nucleus
do not allow [2.8]2+ without diagram
1
(d)
oppositely charged (ions / atoms)
allow positive and negative(ions / atoms)
1
(they) attract
must be in correct context
accept held by electrostatic forces
ignore ionic bonding
maximum 1 if they refer to intermolecular forces / attractions
/ covalent bonds
1
(e)
magnesium chloride
accept MgCl2 (if correctly written)
1
[6]
Page 53
M73.
(a)
C
0.60
H
0.15
O
0.40
1
12
1
= 0.05
= 0.15
16
= 0.025
1
2
6
1
1
C2H6O
1 mark for dividing the correct amount or multiples of correct
amount by Ar
1 mark for proportions
1 mark for whole number ratio – accept any multiple
1 mark for correctly written simplest formula
correct formula without working gets only 2 marks
correct formula gains full marks
provided steps 1 and 2 are correct.
ecf can be allowed from step 2 to 3 or step 3 to 4
formula can be in any order eg OH6C2
1
(b)
intermolecular forces / bonds
1
are weak
(covalent) bonds are weak = 0
or
forces between molecules or bonds between molecules (1)
(attractive) forces are weak = 1
are weak (1)
if no marks awarded, allow low boiling point or small Mr for 1
mark
1
(c)
(i)
to check the safety of the perfume (owtte)
accept references to possible harmful / dangerous effects of
perfume or possible reactions on skin
eg to show it does not damage skin / cause cancer etc.
allow to see what it smells like on the skin
allow so the company do not have to test on animals
1
Page 54
(ii)
any two from:
idea from text linked with an explanation
•
the company claim to have tested the product:
but we cannot be certain they have or how thorough they
are or how accurately reported
•
companies did not disclose how they did their tests:
so they could not be checked or so they could not be
shown to be reliable / valid or so they could not be repeated
or converse
eg companies should disclose how they did their tests so
that results can be checked etc.
•
companies may not have repeated their tests:
so they may not be reliable
•
companies do their own tests:
so they may be biased or so they may not be truthful about their results
or so they may not be reliable
or converse
eg independent tests should be done so as to ensure there
is no bias etc.
•
the companies are using different tests:
so the results cannot be compared or so results will be different or so
results will not be fair / valid / reliable
or converse
eg companies should do the same tests so that the results
will be fair etc.
•
companies would not give false information because of damage to
reputation or it might lead to litigation
2
[9]
M74.
(a)
(i)
any one from:
•
they are positive / cations
•
they are H+
•
opposite charges attract
ignore atom
1
Page 55
(ii)
potassium is more reactive (or reverse)
assume ‘it’ refers to hydrogen
allow potassium reacts with water
allow potassium is very reactive or most reactive metal /
element
allow hydrogen gains electrons more easily / is reduced
more easily
accept potassium is higher up the reactivity series
1
(b)
6 and 2
accept correct multiples and fractions
1
(c)
(i)
the reaction / it is reversible or a description of a reversible reaction
allow ‘it is an equilibrium’
allow reversible symbol drawn correctly
allow ‘the reverse / back reaction’
1
(ii)
lithium nitride
assume that ‘it’ or if they do not specify means lithium nitride
assume lithium / lithium nitrate refers to lithium nitride
•
hydrogen is bonded / held / absorbed / has formed a
compound / reacted with lithium nitride
1
plus one of:
•
does not explode / cause a fire
•
is not free / less hydrogen
•
is not under pressure
•
does not leak
•
is only released slowly
1
•
compound of hydrogen with lithium nitride / product is
(more) stable / less reactive / less chance of a reaction
accept converse for hydrogen as below
assume that gas / hydrogen means gas in the cylinder
•
hydrogen (in cylinder) / gas is not bonded / held
Page 56
absorbed / in a compound / reacted with lithium
nitride
1
plus one of:
•
can explode / cause a fire
•
is free
•
is under pressure
•
can leak
•
releases quickly
1
(d)
(i)
loss of an electron or loses electrons
do not accept any ref. to oxygen
1
(ii)
full outer shell of 8 electrons on circle
need not be paired
can be ×, dot or e
do not accept if extra electrons added to inner shell
1
[10]
M75.
(a)
(i)
any one from:
•
they are positive / cations
•
they are H+
•
opposite charges attract
ignore atom
1
(ii)
potassium is more reactive (or reverse)
assume ‘it’ refers to hydrogen
allow potassium reacts with water
allow potassium is very reactive or most reactive metal /
element
allow hydrogen gains electrons more easily / is reduced
Page 57
more easily
accept potassium is higher up the reactivity series
1
(b)
6 and 2
accept correct multiples and fractions
1
(c)
(i)
the reaction / it is reversible or a description of a reversible reaction
allow ‘it is an equilibrium’
allow reversible symbol drawn correctly
allow ‘the reverse / back reaction’
1
(ii)
lithium nitride
assume that ‘it’ or if they do not specify means lithium nitride
assume lithium / lithium nitrate refers to lithium nitride
•
hydrogen is bonded / held / absorbed / has formed a
compound / reacted with lithium nitride
1
plus one of:
•
does not explode / cause a fire
•
is not free / less hydrogen
•
is not under pressure
•
does not leak
•
is only released slowly
1
•
compound of hydrogen with lithium nitride / product is
(more) stable / less reactive / less chance of a reaction
accept converse for hydrogen as below
assume that gas / hydrogen means gas in the cylinder
•
hydrogen (in cylinder) / gas is not bonded / held
absorbed / in a compound / reacted with lithium
nitride
1
plus one of:
•
can explode / cause a fire
Page 58
•
•
•
•
is free
is under pressure
can leak
releases quickly
1
(d)
(i)
loss of an electron or loses electrons
do not accept any ref. to oxygen
1
(ii)
full outer shell of 8 electrons on circle
need not be paired
can be ×, dot or e
do not accept if extra electrons added to inner shell
1
[10]
Page 59