Cambridge International AS & A Level

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CHEMISTRY9701/34
Paper 3 Advanced Practical Skills 2 October/November 2020

 2 hours

You must answer on the question paper.

You will need: The materials and apparatus listed in the confidential instructions

INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working, use appropriate units and use an appropriate number of significant
figures.
● Give details of the practical session and laboratory, where appropriate,
in the boxes provided. Session

INFORMATION Laboratory
● The total mark for this paper is 40.
● The number of marks for each question or part question is shown
in brackets [ ].
● The Periodic Table is printed in the question paper.
● Notes for use in qualitative analysis are provided in the question paper. For Examiner’s Use

Total

This document has 16 pages. Blank pages are indicated.

IB20 11_9701_34/3RP
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Quantitative Analysis

 ead through the whole method before starting any practical work. Where appropriate, prepare a table
R
for your results in the space provided.

Show your working and appropriate significant figures in the final answer to each step of your calculations.

1 Many hydrated salts lose water of crystallisation when heated.

You will identify the metal in a hydrated salt by heating the salt until it becomes anhydrous.

The equation for the dehydration of the hydrated salt, X•16H2O, is shown.

X•16H2O(s) → X(s) + 16H2O(g)

FB 1 is the hydrated salt, X•16H2O.



(a) Method

●  eigh a crucible with its lid and record the mass.

W
● Add between 1.8 g and 2.0 g of FB 1 to the crucible.
● Weigh the crucible and lid with FB 1 and record the mass.
● Place the crucible on the pipe-clay triangle. Gently heat the crucible and contents for
approximately two minutes with the lid on.
● Remove the lid. Then heat the crucible and contents strongly for approximately four
minutes.
● Replace the lid and leave the crucible and residue to cool for at least five minutes.

While the crucible is cooling, you may wish to begin work on Question 2 or 3.


●  eweigh the crucible and contents with the lid on. Record the mass.
R
● Remove the lid. Heat the crucible and contents strongly for a further two minutes.
● Replace the lid and leave the crucible and residue to cool for at least five minutes. Then
reweigh the crucible and contents with the lid on. Record the mass.
● Calculate and record the mass of FB 1 added to the crucible and the mass of residue
obtained.
I

II

III

IV

[5]

(b) Calculations

(i) Calculate the number of moles of water of crystallisation lost during heating of FB 1.

 moles of H2O lost = .............................. mol [1]

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(ii) Use your answer to (b)(i) to calculate the number of moles of anhydrous residue, X,
produced by the heating in (a).

 moles of X produced = .............................. mol [1]

(iii) Calculate the relative formula mass of X.

 Mr of X = .............................. [1]

(iv) X is the sulfate of a metal in Group 13 of the Periodic Table.

Calculate the relative atomic mass of the metal.

Show your working.

 Ar of the metal = .............................. [1]

(v) Use your answer to (b)(iv) to identify the metal present in X.

 The metal is .............................. . [1]

(c) (i) S
 uggest why the crucible and contents were heated with the crucible lid on for the first
two minutes of the experiment.

..............................................................................................................................................

..............................................................................................................................................

........................................................................................................................................ [1]

(ii) Suggest whether the experiment would be more accurate if you reheated the crucible and
contents strongly for a third time.
Explain your answer.

..............................................................................................................................................

..............................................................................................................................................

........................................................................................................................................ [1]

 [Total: 12]

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2 In this experiment, you will determine the concentration of an alkali. You will mix different volumes
of acid with a fixed volume of alkali and measure the temperature rise that occurs each time.
You will then determine the enthalpy change for the neutralisation of the acid with the alkali.

FB 2 is aqueous sodium hydroxide, NaOH.

FB 3 is 1.95 mol dm–3 sulfuric acid, H2SO4.

(a) Method

● Use the thermometer to measure and record the initial temperature of FB 2.

 initial temperature of FB 2 = .............................. °C

●  upport a plastic cup in the 250 cm3 beaker.

S
● Fill one burette with FB 3. Label this burette FB 3.
● Fill the other burette with distilled water.

Experiment 1
● Use the 10 cm3 pipette to transfer 10.0 cm3 of FB 2 into the plastic cup.
● Add 8.00 cm3 of distilled water from the burette into the plastic cup.
● Add 2.00 cm3 of FB 3 from the burette into the plastic cup.
● Stir the mixture and measure the maximum temperature reached. (You may need to tilt the
cup so that the bulb of the thermometer is completely immersed.) Record the maximum
temperature.
● Empty, rinse and shake dry the plastic cup, ready for use in Experiment 2.

●  epeat this procedure to carry out experiments 2 to 5, using the volumes of FB 2, water and
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FB 3 shown in the table. Record the maximum temperature reached in each experiment.

volume of volume of volume of maximum

experiment
FB 2 / cm3 H2O / cm3 FB 3 / cm3 temperature / °C

1 10.0 8.00 2.00

2 10.0 6.00 4.00

3 10.0 4.00 6.00

4 10.0 2.00 8.00

I
5 10.0 0.00 10.00
II
6 10.0
III

IV
 arry out one further experiment which will enable you to determine more precisely the
C
V minimum volume of FB 3 that gives the highest maximum temperature. This is Experiment 6.
Record the volumes of water and FB 3 and the maximum temperature in the table above.[5]

(b) On the grid opposite, plot a graph of maximum temperature reached on the y-axis and volume
of FB 3 on the x-axis.
 Select a scale on the y-axis which includes a temperature 3.0 °C above the maximum
temperature reached.
Label any points you consider to be anomalous.

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Draw two straight lines of best fit on your graph. The first line is for increasing maximum
I temperature and the second after the maximum temperature was reached.

II Extrapolate the two lines so that they intersect.

III
Use your graph to determine the volume of FB 3 that reacts with 10.0 cm3 of FB 2.
IV
 volume of FB 3 = .............................. cm3
[4]

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(c) (i) C alculate the change in energy when the volume of FB 3 in (b) is neutralised by FB 2,
sodium hydroxide.
Assume that 4.2 J of energy changes the temperature of 1.0 cm3 of solution by 1.0 °C.

 energy change = .............................. J [1]

(ii) Calculate the number of moles of sulfuric acid in the volume of FB 3 in (b).
(If you were unable to answer 2(b), use 5.70 cm3 as the volume of FB 3.)

 moles of H2SO4 = .............................. mol [1]

(iii) C
 alculate the enthalpy change of neutralisation, in kJ mol–1, for 1.00 mol of H2SO4 reacting
with FB 2.

 enthalpy change of neutralisation = ...... ............................. kJ mol–1 [1]

sign value

(iv) Write the equation for the neutralisation of FB 3 with FB 2.
Include state symbols.

........................................................................................................................................ [1]

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(v) Use your answer to (c)(ii) and the information on page 4 to calculate the concentration, in
mol dm–3, of NaOH in FB 2.

 concentration of NaOH in FB 2 = .............................. mol dm–3 [1]

(d) A
 part from using a more accurate thermometer, better insulation or taking more readings,
suggest one modification to the procedure which would make the value for the enthalpy
change of neutralisation calculated in (c)(iii) more accurate.

.....................................................................................................................................................

.....................................................................................................................................................

................................................................................................................................................ [1]

 [Total: 15]

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Qualitative Analysis

Where reagents are selected for use in a test, the name or correct formula of the element or compound
must be given.

At each stage of any test you are to record details of the following:

● colour changes seen

● the formation of any precipitate and its solubility in an excess of the reagent added
● the formation of any gas and its identification by a suitable test.

You should indicate clearly at what stage in a test a change occurs.

If any solution is warmed, a boiling tube must be used.

Rinse and reuse test-tubes and boiling tubes where possible.

No additional tests for ions present should be attempted.

3 The following information about the redox properties of some anions will be helpful.

anion property
nitrite easily oxidised
nitrate cannot be oxidised
sulfite easily oxidised
sulfate cannot be oxidised

FB 4 and FB 5 are solutions each containing one cation and one anion.
Both anions are listed in the Qualitative Analysis Notes.

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(a) Carry out the tests and record your observations in the table.
Use a 1 cm depth of FB 4 or FB 5 in a test-tube for each test.

observations
test
FB 4 FB 5
Test 1
Add an equal volume of
aqueous sodium carbonate.

Test 2
Add aqueous ammonia.

Test 3
Add a few drops of aqueous
barium nitrate (or aqueous
barium chloride).

Test 4
Add an equal volume of dilute
nitric acid. Allow to stand for
one minute, then

add a few drops of aqueous

silver nitrate.

[4]

(b) Carry out the following tests in boiling tubes and record your observations in the table.
Use a 1 cm depth of FB 4 or FB 5 for each test.

observations
test
FB 4 FB 5
Test 1
Add aqueous
sodium hydroxide, then

warm the mixture gently and

carefully, then

add one piece of aluminium

foil to the mixture.

 [3]

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(c) Using the information given at the start of the question, select one further test to enable you to
identify the anions present in each of FB 4 and FB 5.
● State the reagent(s) you will use for this test.
● Explain why this test will enable you to identify the anions in FB 4 and FB 5.
● Carry out your test and record the observations.

reagent(s) ...................................................................................................................................

explanation .................................................................................................................................

.....................................................................................................................................................

observations

 [3]

(d) Write the formulae of the anions and cations present in FB 4 and FB 5.
If the tests you carried out did not allow you to identify the ion, write 'unknown'.

FB 4: cation ......................................................... anion ..........................................................

FB 5: cation ......................................................... anion ..........................................................

[2]

(e) Give the ionic equation for one precipitation reaction you observed when using FB 4.
Include state symbols.

............................................................................................................................................... [1]

 [Total: 13]

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Qualitative Analysis Notes

1 Reactions of aqueous cations

reaction with
ion
NaOH(aq) NH3(aq)

aluminium, white ppt. white ppt.

Al 3+(aq) soluble in excess insoluble in excess

ammonium, no ppt.
–
NH4+(aq) ammonia produced on heating

barium, faint white ppt. is nearly always

no ppt.
Ba2+(aq) observed unless reagents are pure

calcium,
white ppt. with high [Ca2+(aq)] no ppt.
Ca2+(aq)

chromium(III), grey-green ppt. grey-green ppt.

Cr3+(aq) soluble in excess insoluble in excess

copper(II), pale blue ppt. blue ppt. soluble in excess

Cu2+(aq) insoluble in excess giving dark blue solution

green ppt. turning brown on contact green ppt. turning brown on contact
iron(II),
with air with air
Fe2+(aq)
insoluble in excess insoluble in excess

iron(III), red-brown ppt. red-brown ppt.

Fe3+(aq) insoluble in excess insoluble in excess

magnesium, white ppt. white ppt.

Mg2+(aq) insoluble in excess insoluble in excess

off-white ppt. rapidly turning brown off-white ppt. rapidly turning brown
manganese(II),
on contact with air on contact with air
Mn2+(aq)
insoluble in excess insoluble in excess

zinc, white ppt. white ppt.

Zn2+(aq) soluble in excess soluble in excess

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2 Reactions of anions

ion reaction

carbonate, CO2 liberated by dilute acids

CO3 2–

chloride, gives white ppt. with Ag+(aq) (soluble in NH3(aq))

Cl –(aq)

bromide, gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq))

Br (aq)
–

iodide, gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq))

I –(aq)

nitrate, NH3 liberated on heating with OH–(aq) and Al foil

NO3–(aq)

nitrite, NH3 liberated on heating with OH–(aq) and Al foil

NO2–(aq)

sulfate, gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids)
SO42–(aq)

sulfite, gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)
SO3 (aq) 2–

3 Tests for gases

gas test and test result

ammonia, NH3 turns damp red litmus paper blue
carbon dioxide, CO2 gives a white ppt. with limewater (ppt. dissolves with excess CO2)
chlorine, Cl 2 bleaches damp litmus paper
hydrogen, H2 ‘pops’ with a lighted splint
oxygen, O2 relights a glowing splint

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© UCLES 2020
The Periodic Table of Elements
Group
1 2 13 14 15 16 17 18
1 2

H He
hydrogen helium
Key 1.0 4.0
3 4 atomic number 5 6 7 8 9 10

Li Be atomic symbol B C N O F Ne
lithium beryllium name boron carbon nitrogen oxygen fluorine neon
6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

at www.cambridgeinternational.org after the live examination series.

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
16

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3

9701/34/O/N/20
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 114 116
actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv
francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium flerovium livermorium
– – – – – – – – – – – – –

57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
138.9 140.1 140.9 144.4 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232.0 231.0 238.0 – – – – – – – – – – –

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