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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]