chemistry c2 foundation and higher mark scheme · 2014. 4. 22. · page 1 chemistry c2 foundation...
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Chemistry C2 Foundation and Higher Mark Scheme
M1. (a) oxygen / O2 (do not allow air)
for 1 mark 1
(b) idea that (it is a) catalyst / it increases the rate of reaction
for 1 mark 1
(c) water H2O and oxygen / O2 (need both) (in either order)
for 1 mark 1
(d) ammonia / NH3 (do not allow ammonium) (allow ammonium hydroxide / NH4OH or ammonia solution) nitric acid / NHO3
in any order for 1 mark each 2
(e) 14 + 4 + 14 + 48 or Mr = 80
gains 1 mark
but or 35%
gains 2 marks 2
[7]
M2. (a) (must be possible for the gas to enter and displace the water) or other suitable apparatus
• apparatus to collect the gas correctly assembled
for 1 mark
• calibrated collection vessel (award even if diagram is wrong)
for 1 mark 2
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(b) (i) at the start / in the first 1/2 minutes (or any time within this range)
for 1 mark 1
(ii) increase the temperature / use smaller pieces of metal / use more metal / increase the surface area of the metal / add a catalyst / shake the flask / increase the concentration / strength of the acid
for 1 mark 1
(c) (i) 48
for 1 mark 1
(ii) increase the amount of magnesium used
for 1 mark (do not allow increase the amount of acid used)
1
[6]
M3. (a) heat light an exothermic
in any order for 1 mark each 3
(b) oxygen / O2
for 1 mark 1
[4]
M4. (a) lithium = Li
(ignore mass / atomic numbers)
fluorine = F (do not allow if case is incorrect)
for 1 mark each 2
(b) (allow ● or o for electrons)
(allow any positions for the seven electrons added provided
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they are on the outer ring)
for 1 mark 1
(c) (2,8)+ or (2,7)–
(brackets not required) gains 1 mark
but (2,8)–
gains 2 marks 2
[5]
M5. (a) electrons neutrons protons
for 1 mark each 3
(b) mass number no. of neutrons 14 8
for 1 mark each 2
[5]
M6. (a) ideas that
• ref to read the balance / read the mass / weight
• ref to read the stop clock / read the time
• ‘readings’ taken at the beginning and end / at regular intervals
for 1 mark each 2
(b) (i) • loss of carbon dioxide (from the flask) }
(ii) • smaller chips give faster reaction / reaction } mark as a whole
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finishes quicker /dissolved faster [or reverse] }
• smaller chips have a larger surface area }
any 2 for 1 mark each [Allow converse answers]
2
(c) ideas that
• heating increases the speed / energy / vibration of the (acid) particles / marble particles
• (acid) particles collide (with marble chips / (particles)) more frequently / more likely to collide
• reacting particles collide with greater energy / collide faster
• so particles more likely to react [do not accept ‘react faster’]
[Accept ‘atoms’, ‘molecules’ or ‘ions’ instead of ‘particles’ in this question]
any three for 1 mark each 3
[7]
M7. Mg S O4
24 + 32 + 16 (×4) or 64 / evidence of all Ar’s correct [so 24 + 32 + 16 1 mark]
gains 1 mark
but (Mr) = 120 No ECF
gains 2 marks [2]
M8. (a) positive / + / 2
gains 1 mark
but 2+ / ++ / +2
gains 2 marks 2
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(b) Ideas that: 2 Ca2+
Br- [Do not disqualify for "bromine" ions] Ions / They are in the ratio 1:2
any two for 1 mark each 2
[4]
M9. Ca = 40
(OH)2 = (16 + 1)2 or 34
gain 1 mark each
but Mr = 74
gains 3 marks [3]
M10. (a) lead chloride } in any order potassium nitrate }
for 1 mark each 2
(b) lead chloride is solid / a precipitate potassium nitrate is aqueous / in solution / dissolves in water NOT liquid
for 1 mark each 2
(Accept ratio of molecular KNO3 : PbC12 is 2:1 for 2 marks) (do not accept relative number of atoms in each compound)
One is a solid, one is a solution – worth 1 mark [4]
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M11. idea that
• contains nitrogen atoms
• contains hydrogen atoms
• atoms are chemically bonded NOT linked/joined
• ratio of one nitrogen to three hydrogen (atoms) formula of ammonia is NH3
for 1 mark each [4]
M12. (a)
Calcium Phosphorus Fluorine
No of protons 15
No of neutrons 10
No of electrons 20
for 1 mark each 3
(b) (i) gain of electron(s)
from (atoms) (of) calcium
for 1 mark 2
(ii) Ca+
gains 1 mark
but superscript only Ca2+ / Ca ++
gains 2 marks
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2
(c) atoms electrons molecule(s) not compound
each for 1 mark 3
(d) (i) ideas that
• ionic – strong forces between ions
• molecular – weak forces between molecules
each for 1 mark 2
(ii) ideas that
• ionic – ions/charged particles are free to move
• molecular -molecules do not carry a charge
each for 1 mark 2
[14]
##
(a) Fe2 [56 × 2] or 112 O3 [16 × 3] or 48
each gain 1 mark
but Mr = 160
gains 3 marks 3
(b) [Fe2 O3 + 2A1 → 2Fe + A12 O3]
160 → 112 (NB Credit if unworked (or value (or value but should be totalled) from (a)) from (a))
gains 1 mark
but 32 g. of Fe2 O3 → 32/160 × 112
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gains 2 marks
but = 22.4
gains 3 marks 3
[6]
M14. (a) (i) 27
(ii) 13
each for 1 mark 2
(b) each proton has a/1 positive charge and each electron has a/1 negative charge OR electrons and protons have (equal but) opposite charges there are equal numbers of protons and electrons in the atom/ so charges cancel or balance (each other)
each for 1 mark 2
(c)
PARTICLE NUMBER OF PROTONS
NUMBER OF NEUTRONS
NUMBER OF ELECTRONS
Fluorine atom 10
Fluoride atom 9 10
each for 1 mark 3
[7]
M15. (a) (i) lead chloride/product of lead + chloride ions is insoluble (in water)
for 1 mark 1
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(ii) Pb2+ + 2C1¯ → PbC12 *(s)
(allow (Pb)2+ 2 (C1–) )
formula solid state symbol balancing for 1 mark each
3
(b) copper hydroxide Cu(OH)2
each for 1 mark
lead sulphate PbSO4
each for 1 mark
no precipitate
for 1 mark
Allow 1 mark for correct formula Na2SO4 in (i)
Allow 1 mark for correct formula Mg (NO3)2 in (ii)
0 marks for any formula in (iii) 5
[9]
M16. (a) (i) A calcium hydroxide/limewater/Ca(OH)2 not CaOH
(ii) B calcium oxide/Quicklime/CaO
(iii) C hydrogen/H2 (accept correct formulae)/ not H2/H
each for 1 mark 3
(b) (i) idea that electrons are lost (by the calcium atom)
gains1 mark
but two electrons are lost (by the calcium atom)/lose outer electrons to get full shell
gains 2 marks
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calcium ions are 2+
for 1 mark
(ii) electrons are gained (by the oxygen atom)
gains 1 mark
but two electrons are gained (by the oxygen atom)/gain electrons to get full outer shell
gains 2 marks
oxygen ions are 2–
for 1 mark 6
(b) (i)(ii) needs: electron loss/gain number (2) charge (+/–)
(c) idea that they are held together by many/strong forces/bonds a lot of energy/high temperature is required to break these forces/bonds
each for 1 mark 2
[11]
M17. (a) (i) sodium ions and chloride ions
(allow sodium chloride/salt) [not “chlorine”] for 1 mark 1
(ii) sodium ions and chloride ions
(allow sodium chloride/salt) for 1 mark
H + ions (allow hydrochloric acid)
for 1 mark 2
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(b) H+ + OH– → H2O [N.B Na+ and Cl– may also be present] H+ ions from acid OH– ions from alkali
each for 1 mark
[N.B First mark lost if changes on ions not shown] 3
[6]
##
(a) both reactions slow down with time; both reactions produce same volume of hydrogen
each for 1 mark 2
(b) idea rate is faster with powder or idea rate is slower with ribbon
(allow powder completed before ribbon) for 1 mark 1
[3]
- ##
(a) hydrogen
for 1 mark 1
(b) chloride ions are negative; negative ions move to positive electrode
each for 1 mark 2
(c) any one use of chlorine e.g. sterilisation; bleaching; making plastics
any one for 1 mark 1
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[4]
##
(a) sodium ions and chloride ions (not chlorine) allow sodium chloride/salt/common salt
for 1 mark 1
(b) H+ + OH– →H2O H+ from (hydrochloric) acid OH- from alkali/sodium hydroxide lose 1 mark if no charge shown disregard other ions
each for 1 mark 3
[4]
-
M21. (a) same number/six electrons; same number/six protons; react in same way not same element or both carbon
any two for 1 mark each 2
(b) different number of neutrons
gains 1 mark
but or
C has two more neutrons different mass number
gains 1 mark
or
but two mass units bigger
gains 2 marks
C has 8 neutrons while C has 6 neutrons
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gains 2 marks 2
[4]
##
(a) positive
for 1 mark 1
(b) any reference to loss of electrons
for 1 mark
reference to charge being +2 (in (a)) or to loss of 2 electrons (in (b))
for 1 mark 2
[3]
M23. (a) This part was not marked 1
(b) electrolysis 1
because calcium is more reactive (than aluminium or carbon)
accept it is more reactive or very reactive
1
OR
in a blast furnace 1
because calcium is less reactive (than carbon or lower) 1
(c) any equation from
1 mark for correct formulae
1 mark for balancing
2ZnO + C → 2Zn + CO2
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ZnO + CO → Zn + CO2
ZnO + C → Zn + CO 1
[5]
M24. (a) (i) ammonia and hydrogen chloride
both required either order accept formulae if correct in every detail
1
(ii) ammonium chloride / NH4Cl
do not credit ammonia chloride 1
(iii) the fumes / gases / are poisonous / toxic
or ammonia and hydrogen chloride are poisonous / toxic / lethal accept just ammonia is poisonous / toxic accept just hydrogen chloride is poisonous / toxic accept vapour is poisonous / toxic do not credit just fumes are dangerous or harmful
1
(iv) nitrogen
do not credit N/N2
1
hydrogen
do not credit H/H2
1
molecule
do not credit compound or mole 1
covalent
accept single / molecular 1
(b) (i) proton
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neutron
electron
either all three correct
or one or two correct
however do not credit a response which is repeated
2
(ii) protons and neutrons
both required in either order 1
[10]
M25. (a) (i) corners
accept an arrow to any corner 1
(ii) more (surface) exposed
accept can be attacked from more directions or more space around it
1
(b) (i) 1 any two pairs from
more concentrated
answers may be in either order do not accept more acid do not accept more powerful or stronger (but stronger is neutral) a reference to sulphuric acid is neutral
1
more particles to hit the solid
accept more collisions per second do not accept more collisions
1
2 hotter solution or increasing temperature
(faster) particles hit more often or harder
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accept particles have more energy or are more powerful or more successful collisions
1
3 stirring
more surface area exposed or particles available
accept more collisions per second do not accept more collisions
1
(ii) cut it up or increase the surface area
accept grind it up or powder it or flatten it do not accept make it smaller or use a smaller piece
1
more particles are exposed or available or can react
accept heat it and there are more successful collisions for both marks
1
[8]
M26. (a) (i) rings of 2, 8 and 3 electrons
credit 2, 8, 3 pay particular attention to the outer shell in diagrams
1
(ii) rings of 2, 8 and 7 electrons
credit 2, 8, 7 pay particular attention to the outer shell in diagrams
1
(b) (i)
labels not required on atoms charges need to be shown on ions reference to outer shell is required otherwise a maximum of two marks
structure of atoms/ions marks
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(ring of 2, 8, 1 for sodium) or the outer shell of sodium only contains 1 electron
credit 2, 8, 1 or an ion 2, 8 or two circles and 1 electron in outer shell
1
(ring of 2, 6 for oxygen) or outer shell only contains 6 electrons
credit 2, 6 or an ion 2, 8 or two circles 1
transfer of electrons mark
two sodiums needed to supply two outer electrons to oxygen to complete the (one oxygen's) outer shell
award maximum of two marks if a covalent structure is given
credit two rings of electrons for sodium showing outer electrons transferring to outer shell of one oxygen for three marks
do not accept diagrams showing overlapping rings for third mark
1
(ii) loses an electron
credit atoms lose electrons or oxygen takes the electron ignore oil rig
1
[6]
M27. (a) (i) 8
ammonia
do not credit ammonium
sulphuric acid
do not credit just sulphuric; credit sulfuric acid
do not credit hydrogen sulphate 3
(ii) (as a) fertiliser 1
(iii) nitric (acid)
accept HNO3 if correct in every detail
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1
(b) (i) chemical change (in which)
or under suitable conditions 1
product(s) can be converted to reactant(s)
or direction of reaction can be reversed
or equilibrium can be achieved
do not credit reaction can be reversed 1
(ii) air
or (the) atmosphere 1
(iii) made of atoms 1
which are all the same
credit the idea that the particles (in an element) are all the same even if the name of the particles (the first mark) is incorrect
or which have the same number of protons
or which have the same atomic number / proton number
it cannot be broken down into anything simpler (2) marks 1
[10]
M28. NOTE
In this question and throughout the Paper, if the name of a chemical is asked for, then the formula is acceptable only if it is correct in every detail. If the name is correct and the candidate has tried to be ‘helpful’ by giving, in addition, an incorrect version of the formula, then this is acceptable provided it does not lead to ambiguity.
(i) nitric (acid)
accept HN03
1
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(ii) sulphuric (acid)
accept H2SO4
1
(iii) heat given out
or temperature rise
or energy given out
or steam
do not credit just „use a thermometer‟
do not credit just 'change in temperature' 1
(iv) neutralisation
accept neutralise
accept neutral
accept formation of salt or water
do not credit exothermic 1
[4]
M29. (a)
both correct in each row
electron ...– (1)
allow negative 1
1 .......... 0
allow neutral or none 1
proton .....+ (1)
allow positive 1
(b) (i) protons...electrons
both correct in correct order 1
(ii) protons....neutrons
both correct in either order
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1
(c) (i) sodium fluoride
do not credit sodium fluorine 1
NaF
must be correct in every detail
do not credit NAF and the like 1
(ii) ionic
accept ion (bonding)
do not credit ironic or iron (bonding) 1
(iii) electron transferred from sodium to fluorine
accept electron transferred from metal to non-metal
either positive sodium ion and negative fluoride ion
or correctly identified by the symbols Na+ and F- accept „positive sodium ion and negative fluorine ion‟
1
or attracted because have opposite charge(s)
or (atoms/ions) form an (ionic) lattice or (atoms/ions) form a crystal
e.g.
or both marks may be gained by a suitable dot and cross diagram 1
[10]
M30. graph steeper 1
becomes horizontal 1
reaches twice the height, 40 cm3 1 cm3
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1
[3]
M31. (a) proton + (1)
both required
neutron 1
both required
electron – (1)
both required 3
(b) 2.8.3
accept words or diagram to this effect 1
(c) (i) 24 1
(ii) 52 1
(d) any one of
• gains one or more electrons
accept gains an electron
• becomes an anion
do not credit becomes an ion
• becomes a negative ion 1
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(e) sodium ions have a (single) positive charge and chloride ions have a (single) negative charge
do not credit „chlorine ions‟ but
allow this error to be carried forward 1
ions with opposite charge are attracted (to each other)
or the positive ions and the negative ions are attracted (to each other) or the sodium ions and the chloride ions are attracted (to each other)
1
(positive and negative) ions are arranged alternatively (in each direction or dimension)
or ions with the same charge are repelled (by each other) no mark for just ionic bonds
1
[10]
M32. Cl2 + 2Br → 2Cl + Br2
formulae correct for elements 1
correct charge on both ions 1
credit balanced if Cl2 and Br2 included 1
[3]
M33. (a) Zn + 2HC 1 → ZnC12 + H2
1
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(b) (i) 12.5 1
(ii) steeper curve same volume of gas evolved
do not credit two intersects of straight lines
accept a sharp bend 2
(iii) any two from:
stir it
accept mix it better
heat it
accept warm it
use a more finely divided catalyst
accept use a better catalyst or more finely divided zinc
do not credit use acid of a higher 2
(c) (i) any one from
zinc is more reactive than copper
accept zinc is above copper in the reactivity series
zinc displaces copper
accept it is higher than copper in the reactivity series 1
(ii) zinc + copper sulphate → copper + zinc sulphate
ignore the presence of acid or water
accept a balanced equation 1
[8]
M34. (i) (Y) more gas / carbon dioxide given off
1
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(ii) (X) curve / slope steeper
accept rises more rapidly / only took 30 seconds 1
(iii) (flat) since calcium carbonate / substrate all used up
accept the reaction has stopped / no more gas is being produced 1
1
[3]
M35. (i) (Y) more gas / carbon dioxide given off
1
(ii) (X) curve / slope steeper
accept rises more rapidly / only took 30 seconds 1
(iii) (flat) since calcium carbonate / substrate all used up
accept the reaction has stopped / no more gas is being produced 1
1
[3]