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Acids Mark Scheme 1

Level Edexcel

Subject Chemistry

Exam Board GCSE(9-1)

Topic Chemical Changes

Sub Topic Acids

Booklet Mark Scheme 1

Time Allowed: 51 minutes

Score: /42

Percentage: /100


Question Number

Answer Acceptable answers Mark

1(a)(i) electrical (energy) / electricity / direct (electric) current

(1)

Question Number


1(a)(ii) A description including

{light / ignite} gas / lighted

splint (1) gas burns / (squeaky) pop (if

air is present) (1)

reject glowing splint

second mark conditional on first

(2)

Question

Number


1(b) sea water / salt / brine / sodium

chloride (solution)

(1)

Question Number


1(c)(i) D salt and water only (1)

Question Number


1(c)(ii) A description to include two from

(green) solid {disappears /

dissolves} (1)

effervesces / bubbles (ofcolourless gas) given off (1)

blue (solution) forms (1)

ignore references to names of

products

fizz

goes blue ignore incorrect colours of

solution

ignore temperature rise

(2)


Question Number


1(d)(i) An explanation linking

tablet C (1)

because it neutralisesgreatest volume of acid (1)

ignore references to rate

(2)

Question Number


1(d)(ii) {crushed tablets / chewedtablets} have a shorter

reaction time (than wholetablets) (1)

ignore crushed because times are quicker / larger surface area / do

not need to break down

(1)


Question Number


2(a) magnesium nitrate water carbon dioxide

all three correct (2) magnesium nitrate + one other correct (1)

allow correct formulae

(2)

Question Number


2(b)(i) C – neutralisation (1)

Question Number


2(b)(ii) ZnO + 2HCl ZnCl2 + H2O (3)

LHS (1) RHS (1) balancing of correct formula (1)

correct multiples ignore state symbols

(3)


Question Number

Indicative Content Mark

QWCC *2(c) A description including some of the following points

experiment set up hydrochloric acid in container carbon rods in acid attach rods to electrical supply d.c. supply(or reference to positive and negative) test tubes to collect gases

test hydrogen lighted splint squeaky pop (with air)/burns

test chlorine (damp blue) litmus paper (turns red then) bleaches/white

(6)

LevelLev No rewardable content 1 1 – 2 a limited description e.g. simple description/diagram of electrolysis

set up OR description of test for one of the gases. the answer communicates ideas using simple language and uses

limited scientific terminology spelling, punctuation and grammar are used with limited accuracy

2 3 – 4 a simple description e.g. a full description of electrolysis OR testfor both gases OR simple description of electrolysis and the test forone of the gases.

the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately

spelling, punctuation and grammar are used with some accuracy

3 5 – 6 a detailed description e.g. description of electrolysis and test forboth gases OR a full description of electrolysis and of one gas test.

The answer communicates ideas clearly and coherently uses arange of scientific terminology accurately

spelling, punctuation and grammar are used with few errors


Question Number

Answers Acceptable Answers Mark

3 (a) A aluminium nitrate and lead sulfate

(1)

Question Number


3 (b) An explanation linking two of the following

strong (forces of / electrostatic) attraction (1)

(between) oppositely charged ions (1)

requires lot of heat/energy {to separate ions/overcome forces/break bonds} (1)

Any reference to molecules/molecular/intermolecular/covalent scores 0 marks overall

strong bonds ignore “between atoms” for this mark ignore strong lattice / giant structure

positive and negative ions reject between bonds reject charged atoms for this mark

{high / more} {heat / energy}

ignore hard to melt/high temperature needed

(2)

Question Number


3 (c)(i) white {precipitate /solid}

white powder (1)

Question Number


3(c)(ii) BaSO4 + 2KCl (2)

OR

BaSO4 + KCl (1)

SO4Ba / ClK

Ignore incorrect use of case, or use of superscript or large number 4

(2)


Question Number


3(d)(i) C K+

(1)

Question Number


3 (d)(ii) A description linking three of the following

(sequence has to be correct for full marks)

M1 add/mix/react only sodium carbonate (solution) and lead nitrate (solution) (1)

M2 filter (off precipitate) (1)

M3 dep on M2

M3 wash/rinse (solid/residue with distilled water)

OR

dry using {filter paper/paper towel/in a (warm/drying) oven} (1)

add/mix/react the (two) solutions/them

for M1 ignore warm/heat mixture

if any indication of heating to evaporate anywhere only M1 can be scored

if any other reagent added eg acid can score max 2 for question

decant (off the solution)

reject if wash with acid or other reagent

leave to dry / in the sun / on a radiator / near a window reject heat/hot oven

(3)


Question Number


4(a) D aq l (1)

Question Number

Answer acceptable answers Mark

4(b) H+ + OH- (1) H2O (1) LHS (1) RHS (1) ignore state symbols, even if incorrect. allow inclusion of spectator ions, Na+ and Cl-, if shown on both sides for one mark max

(2)

Question Number


4(c)(i) suitable acid-base indicator eg methyl orange, phenolphthalein

litmus reject universal indicator allow recognisable phonetic spelling

(1)

Question Number


4(c)(ii) correct colour change for suitable indicator in 4(c)(i):

methyl orange : yellow orange/pink/red

phenolphthalein : magenta/pink colourless

litmus : blue red

ignore clear (1)

Link 4ci and 4cii together on e-Pen

Question Number


4(d) rel mass NaOH = 23.0 + 16.0 + 1.00 (1)

concentration = 20.0 x 1 (1) formula mass

(= 40.0) (1)

0.5 (mol dm-3) without working (2) (2)


Question Number


4(e) moles of NaOH = 25.0 x 1.50 (1) 1000

(= 0.0375 moles) ratio 1 : 1 / moles NaOH = moles HCl (1)

conc of HCl = 0.0375 x1000 (1) 30.0

(= 1.25 (mol dm-3)) OR 25.0 x 1.50 = 30.0 x conc acid (2)

conc of HCl = 25.0 x 1.50 (1) 30.0 (=1.25 (mol dm-3))

0.0375 (1) – without working shown

conc of HCl = 1.25 (mol dm-3)(3) without any working shown allow ecf

conc = 30.0 x 1.50 = 1.80 (2) 25.0 (mol dm-3)

allow 0.00125 /0.125 / 12.5 max 2

(3)


Acids Mark Scheme 2

Level Edexcel

Subject Chemistry



Sub Topic Acids



Score: /41

Percentage: /100


Question number

Answer Mark

1(a)

• All three correct (2)• Any two correct (1)

salt soluble insoluble ammonium chloride ü lithium sulfate ü magnesium carbonate ü

(2)

Question number

Answer Additional guidance Mark

1(b) • mass values in correct places(1)

• multiplication by 100 (1)• correct final answer to two

significant figures (1)

2.532.85

×100=88.8%

89% (to 2 s.f.) Award full marks for correct numerical answer without working. (3)

Question number

Answer Mark

1(c) An explanation that combines identification – improvement of the experimental procedure (maximum 2 marks) and justification/reasoning, which must be linked to the improvement (maximum 2 marks): • add excess sodium sulfate solution rather than a few drops

(1)• so more reaction occurs to form more lead sulfate (1)• filter the reaction mixture rather than pour off the liquid(1)• so none of the lead sulfate is lost on separation(1)• wash the lead sulfate (1)• so the impurities are removed (1)• place the lead sulfate in an oven/warm place (1)• so the lead sulfate is dry (1) (4)

Question number

Answer Mark

1(d) • volumes of solution too large for titration method (1)• large volumes of liquid need to be heated and then allowed

to crystallise (1) (2)


Question Number


2(a) D a salt and water only (1)

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2(b)(i) A description including two of

• (acid) colourless(liquid/solution) (1)

• (carbonate) green (solid)(1)

• disappears (1)• effervesces/fizzes/bubbles

(1)• blue (solution) (forms) (1)

Ignore clear

dissolves Ignore gas/carbon dioxide given off

(2)

Question Number


2(b)(ii) CuCO3 + 2HNO3 → Cu(NO3)2 + H20 + CO2

reactants (1) products (1) balancing of correct formulae (1)

multiples (3)

Question Number


2(c)(i) An explanation linking

• decomposition (ofcompound/substance) (1)M1

• (by) (direct electric)current (1) M2

splitting up/breaking down/breaking up (of compound/substance) Reject splitting of atoms/elements for M1 Ignore separating

(by) electricity/electrical energy/direct current Reject alternating current/ac

(2)


Question Number


2(c)(ii) A description linking • glowing splint (1) M1

• relights (1) M2

smouldering splint Reject unlit (splint) Ignore blown out (splint) M2 dependent on M1 but lighted splint burns brighter = 2

(2)


Question Number



Reject {ac/ alternating current} (1)

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3(a)(ii) hydrogen H2 (1)

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3(a)(iii) A description including

(damp blue or red) litmus (paper) )

((turns red and) bleached / white )

Allow use of any suitable indicator (1) with correct result (1) eg Universal Indicator (1) is bleached (1) starch-iodide paper (1) turns blue-black (1)

Allow bleaches indicator (1)

Do not allow colourless for {bleached/white} if indicator paper is used

Ignore indicator gets lighter

Ignore any incorrect middle colour mentioned

Ignore smells of swimming pools

(2)

Question Number


3(b) B electrolysis (1)

Question Number


3(c) carbon dioxide CO2 (1)


Question Number


3(d) CuO + 2 HCl → CuCl2 + H2O

2 (1) H2O (1)

Maximum 1 mark if additional incorrect balancing

Reject obvious incorrect symbols and subscripts eg h2O (0) H2O (0) H2o (0) H2O (0) Ignore state symbols

(2)


Question Number


4(a)(i) A carbonate ion CO32- (1)

Question Number



warm / heat / boil (1)

{gas/ammonia} turns (damp red/pink) litmus blue / (damp red/pink) litmus turns blue when held above (the mixture)(1)

maximum (1) if additional reagents added

ignore any ppt

allow pungent smell / smell of {ammonia/wet nappies} /alkaline gas / effect of ammonia on other named indicators /dense white fumes with conc hydrochloric acid

ignore litmus turns blue in ammonium ions/sodium hydroxide/mixture

do not allow gas/ammonia if blue litmus turns red/pink

(2)

Question Number


4(b) Al3+ + 3OH- → Al(OH)3

OH- (1)

Al(OH)3 (1)

balancing 3, conditional on correct formulae (1)

allow multiples

allow HO- (1)

allow Al(HO)3 (1) do not allow Al(HO)3/lower case h

ignore state symbols/3Na+ on both sides

(3)


Question Number


QWCQWC *4(c) An explanation including some of the following points

test for cation • flame test• if the flame is yellow/not lilac, sodium ions are present• if the flame is lilac/not yellow, potassium ions are

present

test for iodide ions

OR

• make a solution of the crystals in water• add dilute nitric acid• add silver nitrate solution• if there is a yellow precipitate, iodide ions are present• if there is no precipitate, sulfate ions are present• Ag+ + I¯ → AgI

• make a solution of the crystals in water• add chlorine water• then cyclohexane• if the cyclohexane/top layer turns purple, iodide ions

were present• if there is no colour change, sulfate ions are present• Cl2 + 2I- → 2Cl- + I2

test for sulfate ions • make a solution of the crystals in water• add dilute {hydrochloric/nitric} acid• add barium {chloride/nitrate} solution• if there is a white precipitate, sulfate ions are present• if there is no precipitate, iodide ions are present• Ba2+ + SO4

2- → BaSO4

(6)

Level 0 No rewardable content 1 1 - 2 • a limited description of test for any 1 ion e.g. flame test, yellow

flame, sodium ions are present.• the answer communicates ideas using simple language and uses

limited scientific terminology• spelling, punctuation and grammar are used with limited

accuracy2 3 - 4 • a simple description to identify a cation and an anion e.g. if the

substance is sodium sulfate, it will give a yellow flame in a flametest and a white precipitate with barium chloride solution.

• the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately

• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed description to identify at least 3 ions e.g. carry out a

flame test, yellow flame, sodium ions present, lilac flame,potassium ions present, add silver nitrate solution to solution ofsubstance, yellow precipitate, iodide ion.

• the answer communicates ideas clearly and coherently uses arange of scientific terminology accurately

• spelling, punctuation and grammar are used with few errors


Acids Mark Scheme 3

Level Edexcel

Subject Chemistry



Sub Topic Acids



Score: /51

Percentage: /100


Question number

Answer Mark

1(a)(i) An explanation that makes reference to: identification – knowledge (1 mark) and reasoning /justification – knowledge (1 mark): • a strong acid is completely ionised in solution/exists

completely as ions (1)• but a weak acid is only partly ionised/exists mainly as

molecules with very few ions present (1) (2)

Question number

Answer Mark

1(a)(ii) hydroxide ions react with hydrogen ions and reduce the hydrogen ion concentration therefore increase pH (1) (1)

Question number

Answer Mark

1(b) ZnO + 2HNO3 → Zn(NO3)2 + 2H2O • zinc nitrate formula (1)• full, balanced equation (1) (2)

Question number


1(c) mass =

4050 × (1) = 2 (g) (1)

1000Award full marks for correct numerical answer without working. (2)


Question Number

Indicative content

1(d) Answers will be credited according to candidate's deployment of knowledge and understanding of the material in relation to the qualities and skills outlined in the generic mark scheme.

The indicative content below is not prescriptive and candidates are not required to include all the material which is indicated as relevant. Additional content included in the response must be scientific and relevant.

AO2 (3 marks) • suitable acid: sulfuric acid• suitable substance : magnesium oxide / magnesium carbonate /

magnesium hydroxide / magnesium• equation for reaction:

MgO + H2SO4 → MgSO4 + H2O/Mg(OH)2 + H2SO4 → MgSO4 + 2H2O/MgCO3 + H2SO4 → MgSO4 + H2O + CO2/Mg + H2SO4 → MgSO4 + H2

AO3 (3 marks) • add solid to warmed acid until in excess solid remains (oxide and

hydroxide) / add solid a little at a time until no more bubbles(carbonate/metal)

• filter off the excess solid, pour remaining solution into an evaporatingbasin

• {heat solution / leave the water to evaporate}• until pure salt crystals form and then dry salt crystals with absorbent

paper/leave to dry.

Level Mark Descriptor 0 No rewardable material.

Level 1 1–2 • The plan attempts to link and apply knowledge and understandingof scientific enquiry, techniques and procedures, flawed orsimplistic connections made between elements in the context ofthe question. (AO2)

• Analyses the scientific information but understanding andconnections are flawed. An incomplete plan that provides limitedsynthesis of understanding. (AO3)

Level 2 3–4 • The explanation is mostly supported through linkage andapplication of knowledge and understanding of scientific enquiry,techniques and procedures, some logical connections madebetween elements in the context of the question. (AO2)

• Analyses the scientific information and provides some logicalconnections between scientific enquiry, techniques andprocedures. A partially completed plan that synthesises mostlyrelevant understanding, but not entirely coherently. (AO3)

Level 3 5–6 • The explanation is supported throughout by linkage andapplication of knowledge and understanding of scientific enquiry,techniques and procedures, logical connections made betweenelements in the context of the question. (AO2)

• Analyses the scientific information and provide logical connectionsbetween scientific concepts throughout. A well-developed planthat synthesises relevant understanding coherently. (AO3)


Question Number


2(a)(ii) • (damp blue) litmus (paper)(1)

• (turns red then) {bleaches/ goes white} (1)

allow bleaches indicator for 1 mark

ignore indicator goes lighter ignore smells of chlorine/swimming pools ignore any incorrect middle colour mentioned

use of suitable named indicator with correct result e.e.(damp) universal indicator paper(1)(turns red then) bleaches (1)

starch-iodide paper(1) turns blue-black(1)

(2)

Question Number


2(a) (iii) poly(chloroethene) PVC/polyvinylchloride/polychloroethene/poly(chlorethene)

(1)

Question Number


2(a)(i) an explanation linking the following

• decomposition (ofcompound/substance/electrolyte)(1)

• using (direct) current (1)

splitting up/breaking down/breaking up

ignore separating

reject splitting of atoms/elements/molecules for M1

using {electrical energy /electricity}

reject alternating current/ac

(2)


Question Number


A2(b)(i)) D gCl(s) (1)

Question Number


2(b)(ii) same/n co hange (1)

Question Number


2(b)(iii) HCl + AgNO3 → AgCl + HNO3

• reactant formulae (1)

• product formulae (1)

Ag+ + Cl- → AgCl

max 1 if any incorrect attempt to balance

reject incorrect use of cases and non-subscripts

(2)


Question

Number


3(a)(i) A calcium ion, Ca2+ (1)

Question Number



white (1)

precipitate/ppt/ppte/solid (1)

Maximum 1 mark if bubbles / fizzing / effervescence also

mentioned

Ignore colour of solution

Ignore cloudy Ignore off white/milky

Allow crystals (1) Ignore powder

Ignore name of precipitate

(2)

Question

Number


3(b) B lead chloride (1)

Question Number


3(c)(i) (barium chloride (aq) + sodium sulfate (aq) →)

sodium chloride (aq) + barium sulfate (s)

sodium chloride (1)

(sodium chloride) (aq) and

barium sulfate (s)both state symbols matched to the

correct product (1)

Allow NaCl (1)

Do not allow sodium chlorine

Accept BaSO4 for barium

sulfate Accept (aq) if sodium chlorine given

Do not allow (solid) Do not allow (AQ)

(2)


Question

Number


3(c)(ii) An explanation linking

{barium sulfate/it} is

{insoluble / does not dissolve}(1)

so it {cannot enter/cannot mix

with/is not absorbed} into the{blood(stream)/body}

orit passes through the body(unchanged) (1)

{barium sulfate/it} does not

dissolve into the blood(stream) (2)

Allow barium is insoluble / does not

dissolve (1) Ignore barium sulfate is a

precipitate

Ignore it cannot be digested

(2)


Question Number


4(a) C (1)

Question Number


4(b) CuCl2 ensure that 2 is subscript at most half the size of Cl and cases are correct

ignore correct charges reject an overall charge

(1)

Question Number


4(c) D (1)

Question Number


4(d) A description including the following

• put/mix/react (sodium)carbonate and acid in(conical) flask (1)

• put limewater in testtube(1)

• (carbon dioxide produced)turns lime water{milky/cloudy/whiteprecipitate} (1)

2 max if reactants and limewater are in the wrong vessels with the correct test

marks can be awarded for the first two marking points by labelling the diagram

“reactants” for sodium carbonate and acid

(3)


Question Number


4(e) A description including three of the following

• make {solutions/dissolve}/{mix/react} solutions (1)

• precipitate (of coppercarbonate) (1)

• filter (1)

• wash (with water) (1)

• leave to dry/dry inoven/dry between filterpaper (1)

max 2 marks if clear error in process, e.g. heat/add acid/evaporate

ignore colours of precipitate accepts forms a solid for precipitate

(3)


Question Number


5(a) D (1)

Question Number


5(b) an explanation linking the following

• decomposition /breakdown of {compound /substance / electrolyte}(1)

• using electricity / electricalenergy / d.c supply (1)

do not allow first point if mention of covalent molecule, substance etc.

note examples in spec are water and Hydrochloric acid

(2)

Question Number


5(c) Cl2 + 2NaOH NaOCl + NaCl + H2O



• balancing correct formulae(1)

allow multiples

(3)


Question Number


QWCQWC *5(c) an explanation linking some of the following:

cause of acid rain • burning sulfur• produces sulfur dioxide• escapes into atmosphere• dissolves in rain water• forming acidic solution / sulfurous / sulfuric acid• falls to the ground as acid rain

effect of acid rain • acidification of lakes• kills fish• kills trees / forests• damage / erosion of stonework

reduction of damage • calcium carbonate• from limestone• may be converted into calcium hydroxide• waste gases from power stations• passed through carbonate or hydroxide• removing sulfur dioxide

some of the above points could be made using word or symbol equations (6)

Level 0 No rewardable content 1 1 - 2 • a limited explanation e.g. when fuels burn the sulfur makes

sulfur dioxide that causes acid rain• the answer communicates ideas using simple language and uses


accuracy2 3 - 4 • a simple explanantion e.g. when the fuel burns, sulfur impurities

make sulfur dioxide which gives acid rain. Acid rain reacts withlimestone statues.


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed explanation e.g. when fuels burn, any sulfur impurities

burn to make sulfur dioxide which dissolves in rain to make itmore acidic. This rain corrodes metals and limestone. Theproblem can be solved by removing sulfur from the fuels




Electrolytic Processes Mark Scheme 1

Level Edexcel

Subject Chemistry



Sub Topic Electrolytic Processes



Score: /43

Percentage: /100


Question Number


1(a)(ii) • (damp blue) litmus (paper)(1)

• (turns red then) {bleaches/ goes white} (1)

allow bleaches indicator for 1 mark

ignore indicator goes lighter ignore smells of chlorine/swimming pools ignore any incorrect middle colour mentioned

use of suitable named indicator with correct result e.e.(damp) universal indicator paper(1)(turns red then) bleaches (1)

starch-iodide paper(1) turns blue-black(1)

(2)

Question Number


1(a) (iii) poly(chloroethene) PVC/polyvinylchloride/polychloroethene/poly(chlorethene)

(1)

Question Number


1(a)(i) an explanation linking the following

• decomposition (ofcompound/substance/electrolyte)(1)

• using (direct) current (1)

splitting up/breaking down/breaking up

ignore separating

reject splitting of atoms/elements/molecules for M1

using {electrical energy /electricity}

reject alternating current/ac

(2)


Question Number


1(b)(i)) A D gCl(s) (1)

Question Number


1(b)(ii) same/n co hange (1)

Question Number


1(b)(iii) HCl + AgNO3 → AgCl + HNO3



Ag+ + Cl- → AgCl

max 1 if any incorrect attempt to balance

reject incorrect use of cases and non-subscripts

(2)


Question Number


2(a)(i) B H+ and Na+ ions (1)

Question Number


2(a)(ii) An explanation linking

• electron(s) (1)

• (have been) lost/removed(1) conditional onelectrons

ignore reference to number of electrons do not allow negative charge

chlorine gains electrons (0) allow chlorine loses electrons (1) (2)

Question Number


2(a)(iii) Any one from

• it contains (excess){hydroxide/OH¯} ions (1)

• {sodium/Na+} ions and{hydroxide/ OH¯} ionsremain (1)

• it is sodiumhydroxide/NaOH (1)

• {hydrogen/H+} ions havebeen removed (at thecathode) (1)

ignore solution has pH greater than 7

allow no hydrogen ions left/acidic ions removed

(1)

Question Number


2(a)(iv) use {molten/liquid} {sodium chloride /electrolyte} / melt {it/sodium chloride/electrolyte}

ignore just liquid/liquid sodium (1)


Question Number


2(b)(i) An explanation linking

Marking point 1 • {hydroxide/OH-} ions

(from water) (1)

Marking point 2 • (ions) lose electrons /are

oxidised (1)

half equation, even unbalanced, showing hydroxide ions losing electrons (2)

do not allow marking point 1 if only {oxygen/sulfate} ions mentioned

(2)

Question Number


2(b)(ii) 1.27 / 63.5 (1) (= 0.02) 0.02 with no working (1)

correct working with incorrect answer (1)

(1)


Question number

Answer Mark

3(a)(i) C (1)

Question number

Answer Mark

3(a)(ii) C (1)

Question number

Answer Mark

3(b) reactants are being used up (1) (1)

Question number

Answer Mark

3(c) An explanation that combines identification via a judgement (1 mark) to reach a conclusion via justification/reasoning (1 mark): • aluminium and copper have different size atoms (1)• and so this prevents the layers of metal atoms from sliding

over one another (1) (2)

Question number


3(d) proportion gold = 9 ÷ 24 (= 0.375) (1)

mass = 0.375 × 12 = 4.5 (g) (1)

Award full marks for correct numerical answer without working.

(2)


Question number

Answer Mark

4(a) An explanation that combines identification – application of knowledge (1 mark) and reasoning/justification – application of understanding (1 mark): • J and K are electrolytes (1)• because their solutions conduct electricity and are

decomposed (1) (2)

Question number

Answer Mark

4(b) D (1)

Question number

Answer Mark

4(c) An explanation that combines identification – understanding (1 mark) and reasoning/justification – understanding (3 marks): • hydrogen (H+) and sodium (Na+) ions attracted to cathode,

hydroxide (OH−) ions and sulfate (SO42−) ions attracted to

anode (1)• because the ions are attracted to the oppositely charged

electrode (1)• 2 hydrogen ions/2 H+ accept 2 e to form

hydrogen molecule/H2 (1)• 4 hydroxide ions/4 OH− lose 4 e to form

oxygen molecule/O2 (1) (4)

Question number

Answer Mark

4(d) Cu2+ + 2e- → Cu

• all species (1)• balancing (1) (2)


Question Number


5(a)(iii) A description including the following

• glowing splint (1)

• relights (1)

smouldering splint Ignore blown out splint

lighted splint burns brighter = 2 (2)

Question Number


5(b)(i) B (1)

Question Number


5(b)(ii) use a fume cupboard/open all the windows /(good) ventilation/wear a gas mask

Ignore do not breathe in

(1)

Question Number


5(c) hydrochloric (acid) Ignore HCl (1)

Question Number


5(a)(i) 2H2O → 2H2 + O2

• reactant formula (1)



Allow 1 mark for 2H2O → 2H2 + O2

Ignore state symbols Ignore word equations

(3)

Question Number


5(a)(ii) A description including the following:

• lighted splint / ignite gas /gas burns( 1)

• with (squeaky) pop (if airpresent) (1)

(2)



Level Edexcel

Subject Chemistry






Score: /48

Percentage: /100


Question Number


1(a)(i) cathode

Reject anode

(1)

Question Number


1(a)(ii) A description to include

ANODE/IMPURE COPPER/ +VE

ELECTRODE becomes smaller/ loses mass /

loses copper / copper atoms form ions / copper is oxidised / copper (ions) enter solution (1)

CATHODE/ PURE COPPER/ -VE

ELECTRODE {red-brown/copper} deposit/

becomes larger / gains mass /

gains copper / copper ions are reduced / copper (ions) from

solution add to electrode (1)

allow half equation

allow half equation

(2)

Question

Number


1(a)(iii) D reduction (1)

Question Number


1(a)(iv) An explanation linking

ions / cations / copper ions / anions / sulfate ions (1)

(are free to) move (in solution) (1)

reject electrons / atoms / molecules ignore ‘charged particles’

allow flow

2nd mark dependent on 1st

MP

(2)


Question Number


QWC *1(b) A description / explanation including some of the following points

marks can be scored from diagrams incorrectly balanced equations can be used as evidence of

reaction occurring but po not otherwise credited electrolysis process

ions move when current passed

negative ions move to anode overall decomposition of water

2H2O → 2H2+O2

Anode/ positive electrode sulphate ions move to anode hydroxide ions move to anode

hydroxide ions lose electrons/oxidation hydroxide ions form oxygen

half equation: 4OH- → O2 + 2H2O + 4e-

half volume gas at this electrode

oxygen test: glowing splint in gas relights

cathode/ negative electrode

sodium ions move to cathode hydrogen ions move to cathode

hydrogen ions gain electrons / reduction hydrogen ions form hydrogen half equation: 2H+ + 2e- → H2

double volume gas at this electrode hydrogen test: lit splint in gas burns/ pops

hence double volume of hydrogen gas

(6)

Level 0 No rewardable content

1 1 - 2 a limited description e.g. states which ions go to which electrode

the answer communicates ideas using simple language and useslimited scientific terminology

spelling, punctuation and grammar are used with limitedaccuracy

2 3 - 4 a simple explanation e.g. explain formation of one product the answer communicates ideas showing some evidence of clarity

and organisation and uses scientific terminology appropriately


3 5 - 6 a detailed explanation e.g. explaining formation of BOTH

products at electrodes the answer communicates ideas clearly and coherently uses a

range of scientific terminology accurately spelling, punctuation and grammar are used with few errors


Question Number


2(a) improves resistance to corrosion ignore rusting (1)

Question Number


2(b) An explanation to include

anode dissolves / half equationgiven / atoms lose electrons/copper becomes ions/copper(atoms) oxidised (1)copper ions moving fromanode to cathode (1)

copper plated on cathode /half equation given / ions gainelectrons/copper ionsreduced/copper ions formatoms (1){difference/0.2g} is impurities(1)

would expect same decreasein mass (as increase) (1)

ignore references to mass increase of cathode and mass decrease of anode

ignore ‘impure copper (ions)’ for the second marking point

allow difference is metal around it eaten away/ impurities/sludge fallen to bottom of container /under anode (1) (there needs to be a reference to the difference in electrode masses for this point)

(3)

Question Number


2(c) 2O2- O2 + 4e(-) (2)

OR O2- O + 2e(-) (1) 2O O2 (1)

Unbalanced equation (1)

(2)


Question Number


QWCQWC *2(d) A description including some of the following points

sodium chloride is melted and ions are free to move

at cathode {sodium / positive} ions move to cathode (sodium) metal forms at cathode sodium ions gain electrons ... to form atoms this is reduction Na+ + e- Na

at anode {chloride / negative} ions move to anode (chlorine) gas forms at anode chloride ions lose electrons ... to form atoms this is oxidation two chlorine atoms combine to form a chlorine molecule /

share electrons Cl- Cl + e- / 2Cl- Cl2 + 2e-

2 Cl Cl2 (6)

Levelvel No rewardable content 1 1 - 2 a limited description e.g. gives at least one relevant description

or explanation the answer communicates ideas using simple language and uses

limited scientific terminology spelling, punctuation and grammar are used with limited

accuracy2 3 - 4 a simple description e.g. for anode or cathode gives at least

three descriptions or relevant explanations the answer communicates ideas showing some evidence of clarity

and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy

3 5 - 6 a detailed description e.g. for both anode and cathode gives atotal of at least five descriptions or relevant explanations

the answer communicates ideas clearly and coherently uses arange of scientific terminology accurately



Question Number


3(a)(i) toxic / poisonous (gas) Ignore other words such as harmful / dangerous / smelly / corrosive (1)

Question Number


3(a)(ii) A description including the following points

• (damp blue) litmus (paper)(1)

• (turns red then) white /bleaches (1)

Allow use of any suitable named indicator with correct result eg • (damp) universal indicator paper

(1)• (turns red then) white (1)OR• (damp) starch iodide paper (1)• (turns) dark blue / black (1)

(2)

Question Number


3(a)(iii) making {poly(chloroethene / PVC / solvents / medicines / agrochemicals / disinfectants}

bleach / sterilising water / killing bacteria

ignore water purification / “swimming pools”

micro-organisms

(1)

Question Number


3(a)(iv) 2NaCl + 2H2O → 2NaOH + H2 + C 2

correct products (1) balancing of correct formulae (1)

NaCl + H2O → NaOH + ½ H2 + ½ Cl2

(2)


Question Number


QWC *3(b) A comparison including some of the following points

Comparing volumes of hydrogen and oxygen • (in each experiment) volume of hydrogen is twice volume of

oxygen• because water molecules contain twice as many hydrogen

atoms as oxygen atoms / is H2O• overall 2H2O → 2H2 + O2

Relating volumes of gases to current and time • (from experiments 1 and 2) time doubles• (from experiments 1 and 2) volumes of gases double• Volumes of gases are directly proportional to the time for

electrolysis / passage of current• (from experiments 1 and 3) as current x 1.5• (from experiments 1 and 3) volumes of gases x 1.5• volumes of gases are directly proportional to the current (6)

Level 0 No rewardable content 1 1 - 2 • a limited description of one trend e.g. increased time gives an

increased gas volume• the answer communicates ideas using simple language and uses

limited scientific terminology• spelling, punctuation and grammar are used with limited accuracy

2 3 - 4 • a simple description e.g. if the time is doubled, the volume of gas isdoubled and if the current is increased the volume of gas increases


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed description e.g. volume of hydrogen is twice volume of

oxygen and as time doubles, volume of gas doubles or as current x1.5, volume of gas x 1.5

• the answer communicates ideas clearly and coherently uses a rangeof scientific terminology accurately



Question Number


4(a) D (1)

Question Number


4(b) an explanation linking the following

• decomposition /breakdown of {compound /substance / electrolyte}(1)

• using electricity / electricalenergy / d.c supply (1)

do not allow first point if mention of covalent molecule, substance etc.

note examples in spec are water and Hydrochloric acid

(2)

Question Number


4(c) Cl2 + 2NaOH NaOCl + NaCl + H2O




allow multiples

(3)


Question Number


QWCQWC *4(d) an explanation linking some of the following:

cause of acid rain • burning sulfur• produces sulfur dioxide• escapes into atmosphere• dissolves in rain water• forming acidic solution / sulfurous / sulfuric acid• falls to the ground as acid rain

effect of acid rain • acidification of lakes• kills fish• kills trees / forests• damage / erosion of stonework

reduction of damage • calcium carbonate• from limestone• may be converted into calcium hydroxide• waste gases from power stations• passed through carbonate or hydroxide• removing sulfur dioxide

some of the above points could be made using word or symbol equations (6)

Level 0 No rewardable content 1 1 - 2 • a limited explanation e.g. when fuels burn the sulfur makes

sulfur dioxide that causes acid rain• the answer communicates ideas using simple language and uses


accuracy2 3 - 4 • a simple explanantion e.g. when the fuel burns, sulfur impurities

make sulfur dioxide which gives acid rain. Acid rain reacts withlimestone statues.


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed explanation e.g. when fuels burn, any sulfur impurities

burn to make sulfur dioxide which dissolves in rain to make itmore acidic. This rain corrodes metals and limestone. Theproblem can be solved by removing sulfur from the fuels





Level Edexcel

Subject Chemistry






Score: /32

Percentage: /100


Question Number



(1)

Question Number



{light / ignite} gas / lighted

splint (1) gas burns / (squeaky) pop (if

air is present) (1)

reject glowing splint

second mark conditional on first

(2)

Question

Number


1(b) sea water / salt / brine / sodium

chloride (solution)

(1)

Question Number


1(c)(i) D salt and water only (1)

Question Number


1(c)(ii) A description to include two from

(green) solid {disappears /

dissolves} (1)

effervesces / bubbles (ofcolourless gas) given off (1)

blue (solution) forms (1)

ignore references to names of

products

fizz

goes blue ignore incorrect colours of

solution

ignore temperature rise

(2)


Question Number


1(d)(i) An explanation linking

tablet C (1)

because it neutralisesgreatest volume of acid (1)

ignore references to rate

(2)

Question Number


1(d)(ii) {crushed tablets / chewedtablets} have a shorter

reaction time (than wholetablets) (1)

ignore crushed because times are quicker / larger surface area / do

not need to break down

(1)


Question Number


2(a) magnesium nitrate water carbon dioxide

all three correct (2) magnesium nitrate + one other correct (1)

allow correct formulae

(2)

Question Number


2(b)(i) C – neutralisation (1)

Question Number


2(b)(ii) ZnO + 2HCl ZnCl2 + H2O (3)

LHS (1) RHS (1) balancing of correct formula (1)

correct multiples ignore state symbols

(3)


Question Number


QWCC *2(c) A description including some of the following points

experiment set up hydrochloric acid in container carbon rods in acid attach rods to electrical supply d.c. supply(or reference to positive and negative) test tubes to collect gases

test hydrogen lighted splint squeaky pop (with air)/burns

test chlorine (damp blue) litmus paper (turns red then) bleaches/white

(6)

LevelLev No rewardable content 1 1 – 2 a limited description e.g. simple description/diagram of electrolysis

set up OR description of test for one of the gases. the answer communicates ideas using simple language and uses

limited scientific terminology spelling, punctuation and grammar are used with limited accuracy

2 3 – 4 a simple description e.g. a full description of electrolysis OR testfor both gases OR simple description of electrolysis and the test forone of the gases.

the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately


3 5 – 6 a detailed description e.g. description of electrolysis and test forboth gases OR a full description of electrolysis and of one gas test.

The answer communicates ideas clearly and coherently uses arange of scientific terminology accurately



Question Number


3(a) D a salt and water only (1)

Question Number


3(b)(i) A description including two of

• (acid) colourless(liquid/solution) (1)

• (carbonate) green (solid)(1)

• disappears (1)• effervesces/fizzes/bubbles

(1)• blue (solution) (forms) (1)

Ignore clear

dissolves Ignore gas/carbon dioxide given off

(2)

Question Number


3(b)(ii) CuCO3 + 2HNO3 → Cu(NO3)2 + H20 + CO2

reactants (1) products (1) balancing of correct formulae (1)

multiples (3)

Question Number


3(c)(i) An explanation linking

• decomposition (ofcompound/substance) (1)M1

• (by) (direct electric)current (1) M2

splitting up/breaking down/breaking up (of compound/substance) Reject splitting of atoms/elements for M1 Ignore separating

(by) electricity/electrical energy/direct current Reject alternating current/ac

(2)


Question Number


3(c)(ii) A description linking • glowing splint (1) M1

• relights (1) M2

smouldering splint Reject unlit (splint) Ignore blown out (splint) M2 dependent on M1 but lighted splint burns brighter = 2

(2)

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Acids - Merit Tutors