Chemistry 9701/33 May/June 2020: question paper and mark scheme
Cambridge AS & A Level Chemistry (9701), Paper 3 Paper 33 (Advanced Practical Skills 1), May/June 2020. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
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
Mark scheme
1(a) I Initial and final burette readings and volume added recorded for rough titre and accurate titre details tabulated. 1
II Initial and final burette readings recorded and vol of FA 2 added recorded for each accurate titration. 1
Headings and units correct for accurate titrations.
Headings: initial/final (burette) reading / volume or reading / volume at start/ finish
and
volume/ FA 2 added/used or titre
and
units (cm3) or / cm3 or in cm3 or cm3 by every entry
III All accurate burette readings are recorded to the nearest 0.05 cm3. 1
IV The final accurate titre recorded is within 0.1 cm3 of any other accurate titre. 1
V, VI and VII 3
Award V, VI and VII for δ ⩽ 0.20 cm3
Award V and VI for 0.20cm3 < δ ⩽ 0.30 cm3
Award V for 0.30 cm3 < δ ⩽ 0.50 cm3
1(b) Calculation of mean 1
Candidate must average two (or more) accurate titres where the total spread is ⩽ 0.20 cm3.
Working must be shown or ticks must be put next to the two (or more) accurate readings selected.
1(c)(i) 0.105 × vol in (b) 1
Correctly calculates moles of FA 2 = correct to 3–4 sf but do not penalise more than once in this question.
1000
1(c)(ii) Moles in 25.0 cm3 = same as (i) 1
and
shows moles in 1 dm3 answer × 40 (3–4 sf)
1(c)(iii) 6.20 1
Uses Mr =
moles from (ii)
1(c)(iv) Chooses acid with Mr nearest to that found 1
and
explains choice
HCOOH = 46; CH2=CHCOOH = 72 C2H4ClCOOH = 111.5
1(d) Add bromine / acidified (or alkaline) potassium manganate(VII) and CH2CHCOOH decolourises (turns green) 1
but
C2H5COOH does not
1(e) (Volume of alkali doubled) → moles of acid doubled 1
→ Mr halved 1
Allow 1 for volume of alkali more → more moles acid → Mr less
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–
Mark scheme
2(a) Table with headings and units. 1
Headings for initial T FA 3, initial T FA 4, average initial T, highest T, T rise.
Experiments 1 and 2 clearly shown.
All thermometer readings to .5 °C 1
Correct calculation of average initial Ts and T rises 1
Both T rises for Experiments 1 and 2 within 1 °C of each other 1
2(b)(i) Correctly calculates 50 × 4.2 × T rise from Expt 1 and answer to 2–4 sf 1
2(b)(ii) 120.1 1
Correctly uses moles FA 3 = (= 0.9844)
122
answer 1
Correctly calculates = 0.0246 (= 0.025) mol
40
2(b)(iii) (i) 1
Correctly uses (to 2–4 sf)
1000 × (ii)
and
negative sign
2(c) Correctly calculates 1
0.5 0.5
Expt 1 + × 100 = 4%
25 25
0.5 0.5 0.5 1
Expt 2 + + = 5%
50 25 25
2(d) With HCl T rise more (comparison needed) 1
In organic acid some energy needed to break O–H bond / to release H+ (from the molecule) 1
FA 5 is HCOOH FA 6 is CH3CHO or C2H5CHO FA 7 is CH3C=OCH3 FA 8 is MgSO4.7H2O
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
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
12
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
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 – – – – – – – – – – –
Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge
Mark scheme
3(a)(i) Award one mark for every two correct observations (*) as shown in table below 5
test FA 5 FA 6 FA 7
+ Mg Fizz / bubbling / effervescence * No visible reaction / no change * No visible reaction / no change *
Gas / hydrogen pops with lighted splint *
+ Tollens’ Silver mirror / black / dark grey solid * Silver mirror / black / dark grey solid * No visible reaction / no change *
+ MnO4‒/H+ (Purple) decolourised * (Purple) decolourised * No visible reaction / no change / remains
purple *
3(a)(ii) FA 5 = (carboxylic) acid / COOH / RCOOH 1
FA 6 = aldehyde / CHO / RCHO 1
FA 7 = ketone / RC=OR / RCOR / RCOR/ 1
3(b)(i) Steam / condensation / water vapour 1
and
white residue / leaves white solid / solid remains white
3(b)(ii) Chooses (aqueous) NaOH 1
and (aqueous) NH3
and indicates use of a solution of FA 8 / FA 8(aq)
NaOH white ppt * insol in excess*
NH3 white ppt* insol in excess*
3(b)(iii) Mg2+ 1
Do not allow magnesium / Mg
Checked your answers against these? Let AI mark the whole paper, on your own working.
Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.
Check your answers against it
Done this paper? Upload your script and CIE Buddy's AI marker marks it question by question against this exact scheme, puts the ticks on your own working and says what each lost mark needed.
Where can I find the 9701/33 May/June 2020 mark scheme?+
On this page, free: the mark scheme for AS & A Level Chemistry 9701/33, May/June 2020 (9701_s20_ms_33), and the question paper (9701_s20_qp_33), to read or download, with each question's marking points written out underneath.
How many marks is 9701/33 out of?+
Chemistry 9701/33 for May/June 2020 is out of 40 marks.
Can I get my 9701/33 answers marked?+
Yes. Upload your answers to 9701/33/M/J/20 as a PDF or photos, and CIE Buddy marks every question against this paper's official mark scheme, using Cambridge's marking rules. You get your score, each lost mark explained on your own script, and the topics to revise. It's a guide, not an official Cambridge grade.