M1.
(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
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]
M2.
five ideas from the following for one mark each
•
each carbon / atom joined / bonded to three other carbon / atomsor each carbon forms 3
bonds
•
in layers
•
only weak forces (of attraction) / bonds between layers
allow weak electrostatic / intermolecular forces /bonds between
layers
•
layers / atoms can slide over each other
•
one electron on each carbon is not used for bonding
•
electrons delocalised or electrons free
allow ‘sea’ of electrons
•
electrons carry the charge / current
•
giant structure / lattice
•
covalent (bonds)
•
strong bonds or a lot of energy needed to break bonds
reference to ionic bonding = max 4
diagrams could be used:
•
to show layered structure
•
to show that each carbon is bonded to three other
atoms
•
to show giant structure (at least 3 rings required)
carbon
[5]
##
(a)
potassium / K
for 1 mark
1
(b)
carbon dioxide / CO2
for 1 mark
1
(c)
losing
electrons
gaining
electrons
for 1 mark each
4
(d)
(i)
power supply, (not mains) beaker containing solution,(inert) electrodes and
circuitammeter 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]
M4.
(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
(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 theyare or how accurately reported
•
companies did not disclose how they did their tests:so they could not be
checked or so they could not beshown to be reliable / valid or so they could
not be repeated
or converseeg 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 converseeg 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 converseeg companies should do the same tests so that the
results will be fair etc.
•
companies would not give false information because of damage to
reputationor it might lead to litigation
2
[9]
M5.
(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
different number of neutrons
accept different mass numbers
do not accept different atomic masses
1
[4]
M6.
(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
(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]
M7.
(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]
M8.
(a)
40 + 12 + (3 × 16) = 100
each for 1 mark
2
(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]
M9.
(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
(d)
fastersame final mass
for 1 mark each
2
[12]
M10.
(a)
electrolytes
1
(b)
oxidation
1
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]
M11.
(a)
any two from:
•
outer shell electrons / electrons inhighest energy level (in metals)
•
electrons are delocalised / sea of electrons
•
electrons are free or electrons move aroundor electrons are free to
flow or electronsattracted to positive terminal
•
electrons carry charge / current or electronsform the current / electrons transfer
charge / electronspass charge
ignore electrons carry electricity
ignore reference to positively charged atoms / ions
if they state electrons have +ve charge = max 1 mark
if they state covalent bonding then max 1 mark
2
(b)
ions can move / are attracted to electrode
accept ions are free
allow ‘they’ for ions
or
attracted to named electrode
or
ions are charged or ions form / carry
the current or ions form the charge
1
(c)
(i)
electron gain
ignore hydrogen reduces charge
1
(ii)
sodium hydroxide or NaOH or caustic soda
do not allow hydroxide alone
1
(iii)
2Cl– ─ 2 e– → Cl2
or
2Cl– → Cl2 + 2 e–
allow fractions or multiples
allow e or e–
do not allow e+
1
[6]
(a) 2Cl– – 2e– → Cl2
(allow unaltered LHS to produce ½ Cl2)
Na+ + e– → Na
(allow × 2 for all terms)
M12.
(credit candidates who point out that hydrogen / H2 is in fact produced)
for 1 mark each
2
(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]
M13.
(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.)
equations even if not
correctly balanced
any 1 for 1 mark
allow
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]
M14.
(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 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
•
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]
##
(a)
potassium / K
for 1 mark
1
(b)
carbon dioxide / CO2
for 1 mark
1
(c)
losing
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]
M16.
(a)
(i)
hydrogen/H2
for 1 mark
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
for 1 mark
1
(c)
(i)
zinc carbonate/ZnCO3/zinchydroxide/Zn(OH)2
for 1 mark
1
(ii)
It is insoluble
zinc carbonate is insoluble in water
for 1 mark
1
[13]
M17.
(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 ofenergy / reaction has a high
activation energy
•
gives a better / faster rate of reaction
•
the reaction is endothermic / more energy needed tobreak existing bonds than to
form new ones
allow a higher temperature gives a greater yield / pushesthe
equilibrium position to the right
any two for 1 mark each
2
(f)
ammonia (solution) / ammonium hydroxide
(credit NH3
NH4OH)
nitric acid / HNO3
in any order for 1 mark each
2
[10]
M18.
(a)
one nitrogen atom joined to three hydrogen atoms
1
correct pairs of electrons
1
(b)
because ammonia is made of small molecules / simple
molecules / simple molecular structures
1
and so there are weak forces between the molecules
or and so the intermolecular forces are weak
1
incomplete answers that link only size of molecule or strength of
intermolecular forces with boiling point only gain 1 mark
(c)
(i)
hydroxide
1
(ii)
nitric
1
(d)
because this is an endothermic reaction
1
that takes in energy from the surroundings as the ammoniumnitrate dissolves
1
[8]
M19.
(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
1
OH (aq)
if spectator ions correctly included on both sides, maximum
= 1mark
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]
M20.
(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
(d)
faster
same final mass
for 1 mark each
2
[12]