19th – 29th July 2018
Bratislava, SLOVAKIA
Prague, CZECH REPUBLIC
www.50icho.eu

PRACTICAL PROBLEMSCountry:
Name as in passport:
Student code:
Language:50th IChO 2018
International Chemistry Olympiad
SLOVAKIA & CZECH REPUBLICBACK TO WHERE IT ALL BEGAN

XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

General instructions•

This practical exam booklet contains 28 pages.

•

Before the start of the exam, you will have additional 15 minutes to read the exam booklet.
Do not work, write or calculate during this time, otherwise you will be disqualified.

•

You may begin working as soon as the Start command is given.

•

You have 5 hours to complete the exam.

•

You may work on the tasks in any order, but starting with Problem P1 is recommended.

•

All results and answers must be clearly written in pen in their respective designed areas on theexam papers. Answers written outside the answer boxes will not be graded.

•

Do not use a pencil or a marker to write the answers. Use only the pen and calculator provided.

•

You were provided with 3 sheets of scratch paper. If you need more, use the backside of theexam sheets. Remember that nothing outside the designed areas will be graded.

•

The official English version of the exam booklet is available upon request and serves forclarification only.

•

If you need to leave the laboratory (to use the toilet or have a drink or snack), tell your lab
assistant. He or she will come to accompany you.

•

You must follow the safety rules given in the IChO regulations. If you break the safety rules,
you will receive only one warning from the lab assistant. Any safety rule violations after the firstwarning will result in your dismissal from the laboratory and 0 marks for the entire practicalexamination.

•

Chemicals and labware, unless otherwise noted, will be refilled or replaced without penalty only
for the first item. Each further incident will result in the deduction of 1 point from your 40 practicalexam points.

•

The lab assistant will announce a 30 minute warning before the Stop command.

•

You must stop your work immediately when the Stop command is announced. Failure to stop
working or writing by one minute or longer will lead to nullification of your practical exam.

•

After the Stop command has been given, a lab assistant will come to sign your answer sheet.
After both the assistant and you sign, place this exam booklet back in the exam envelope andsubmit it for grading together with your products and TLC plates.

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Lab rules and safety•

You must wear a lab coat and keep it buttoned up. Footwear must completely cover the foot and
heel.

•

Always wear safety glasses or prescription glasses when working in the lab. Do not wear contactlenses.

•Do not eat or drink in the lab. Chewing gums are not allowed.

•

Work only in the designed area. Keep your work area and the common work areas tidy.

•

No unauthorized experiments are allowed. No modification of the experiments is allowed.

•

Do not pipet with your mouth. Always use a bulb pipette filler.

•

Clean up spills and broken glassware immediately from both the bench and the floor.

•

All waste must be properly discarded to prevent contamination or injury. Non-hazardous watersoluble/miscible lab waste is eligible for sink disposal. Other lab waste must be disposed of ina marked capped container.

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Definition of GHS hazard statements
The GHS hazard statements (H-phrases) associated with the materials used are indicated in the
problems. Their meanings are as follows.
Physical hazards
H225 Highly flammable liquid and vapour.
H226 Flammable liquid and vapour.
H228 Flammable solid.
H271 May cause fire or explosion; strong oxidizer.
H272 May intensify fire; oxidizer.
H290 May be corrosive to metals.
Health hazards
H301 Toxic if swallowed.
H302 Harmful if swallowed.
H304 May be fatal if swallowed and enters airways.
H311 Toxic in contact with skin.
H312 Harmful in contact with skin.
H314 Causes severe skin burns and eye damage.
H315 Causes skin irritation.
H317 May cause an allergic skin reaction.
H318 Causes serious eye damage.
H319 Causes serious eye irritation.
H331 Toxic if inhaled.
H332 Harmful if inhaled.
H333 May be harmful if inhaled.
H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled.
H335 May cause respiratory irritation.
H336 May cause drowsiness or dizziness.
H351 Suspected of causing cancer.
H361 Suspected of damaging fertility or the unborn child.
H371 May cause damage to organs.
H372 Causes damage to organs through prolonged or repeated exposure.
H373 May cause damage to organs through prolonged or repeated exposure.
Environmental hazards
H400 Very toxic to aquatic life.
H402 Harmful to aquatic life.
H410 Very toxic to aquatic life with long lasting effects.
H411 Toxic to aquatic life with long lasting effects.
H412 Harmful to aquatic life with long lasting effects.

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Chemicals
For all problems
ChemicalsLabelled as

Deionized water in:
Wash bottle (bench)
Plastic bottle (bench)
Plastic canister (hood)

Water

GHS hazard statements1

Not hazardous

For Problem P1 (in white basket if not stated otherwise)
Chemicals
Ethanol, 100 cm3 in wash bottle (bench)
2-Acetonaphthone:ca. 0.002 g in glass vial, standard for TLC
0.500 g in glass vial

Labelled as
EthanolStandard A
Reactant A

GHS hazard statements1
H225, H319
H302, H315, H319, H335,
H411

2,4-Dinitrophenylhydrazine, containing 33% (w/w) of
water, 0.300 g in glass vial

DNPH

H228, H302

Bleach solution, containing 4.7% of NaClO, 13.5 cm3 inamber glass bottle

BleachH290, H314, H400

Ethyl acetate, 15 cm3 in amber glass bottle

EtOAc

H225, H319, H336

Eluent for thin layer chromatography, hexanes/ethyl
acetate 4:1 (v/v), 5 cm 3 in amber glass bottle

TLC eluent

H225, H304, H315, H336,
H4112

5% Na2CO3, aqueous solution, 20 cm 3 in plastic bottle

5% Na2CO3

H319

20% HCl, aqueous solution, 15 cm3 in plastic bottle

20% HCl

H290, H314, H319, H335
and others

Labelled as

GHS hazard statements1

For Problem P2 (in green basket)
Chemicals
8 mmol dm−3 luminol in 0.4 mol dm−3 NaOH aqueous
solution, 50 cm3 in plastic bottle

Luminolin NaOH

2.00 mmol dm−3 CuSO4 aqueous solution, 25 cm3 inplastic bottleCu

2.00 mol dm−3 H2O2 aqueous solution, 12 cm 3 in small
plastic bottle

H2O2 conc.

H302, H315, H318

0.100 mol dm−3 cysteine hydrochloride aqueous
solution, 12 cm3 in small plastic bottle

Cys conc.

Not hazardous

Water

Not hazardous

Water, 50 cm3 in plastic bottle

H290, H315, H319
Not hazardous

1 See page 3 for the definition of the GHS hazard statements.
2 The GHS hazard statements for hexanes.

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

For Problem P3 (in grey basket if not stated otherwise)
Chemicals

GHS hazard statements1

Labelled as

Sample of mineral water, 400 cm3 in plastic bottle(bench)SampleNot hazardous

3 mol dm−3 NH4Cl / 3 mol dm−3 NH3 solution in water,
15 cm3 in plastic bottle

Buffer

H302, H319, H314, H400

NaCl, solid, 10 g in plastic bottle

NaCl

H319

Eriochrome black T, indicator mixture in plastic bottle

EBT

H319

Bromothymol blue, indicator solution in plastic bottle

BTB

H302, H315, H319

5.965 × 10−3 mol dm−3 disodium ethylenediamine
tetraacetate standard solution, 200 cm3 in plastic bottle(bench)EDTA

H302, H315, H319, H335

0.2660 mol dm−3 NaOH standard solution, 250 cm3 inplastic bottle (bench)

NaOH

H314

Strong acidic cation exchange resin, in H+ form, 50 cm3of swollen material washed with deionized water in plastic
bottle

Catex

H319

Equipment
For all problems (on shelf if not stated otherwise)
Shared equipment
Paper wipes

Quantity
1 box for 2–4

Waste paper basket (bench, close to sink)
Nitrile gloves (hood)

1 for 4
1 box for lab

Personal equipment
Safety goggles

1

Pipette stand (bench)

1

Bulb pipette filler

1

Glass beaker, 100 cm3, containing: glass rod, plastic spoon,
spatula, tweezers, marker, pencil, ruler

1 (each)For Problem P1 (in white basket if not stated otherwise)
Shared equipment
UV lamp (hood)

Quantity
1 for up to 12

Vacuum source (plastic stopcock with vacuum hose, bench)

1 for 2

Personal equipment
Hotplate stirrer (bench) with:
Temperature probe,
Crystallizing dish, with metallic clip
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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Laboratory stand (bench) with:
Clamp holder with small clamp
Clamp holder with large clamp

1 (each)Organic waste plastic bottle (bench)

1

Open metal ring1

Round bottom flask, 50 cm3, with magnetic stir bar

1

Measuring cylinder, 10 cm 3

1

Reflux condenser

1

Separatory funnel, 100 cm 3, with stopper

1

Erlenmeyer flask without ground joint, 50 cm3

1

Erlenmeyer flask without ground joint, 25 cm3

1

Erlenmeyer flask with ground joint, 50 cm3

1

Glass funnel

1

Suction flask, 100 cm3

1

Rubber adapter for filter funnel

1

Fritted glass filter funnel, porosity S2 (white label)

1

Fritted glass filter funnel, porosity S3 (orange label)

1

Glass beaker, 50 cm3, with Petri dish lid

1

Glass beaker, 150 cm3

1

TLC graduated capillary spotter, 5 l

3Zipped bag with 5 pH indicator strips and 1 pH scale

1

Zipped bag with 2 TLC plates

1

Glass Pasteur pipette

4

Rubber bulb

1

Glass vial labelled Student code B for the product of thehaloform reaction

1

Glass vial labelled Student code C for the product of thereaction with Brady’s reagent

1

For Problem P2 (in green basket if not stated otherwise)
Personal equipment

Quantity

Stopwatch

1

Digital thermometer and card with its calibration constant

1

Volumetric flask, 50 cm3

1

Bulb pipette, 5 cm3 (bench, in pipette stand)1

Graduated pipette, 5 cm 3 (bench, in pipette stand)3

Graduated pipette, 1 cm 3 (bench, in pipette stand)2

Plastic bottle labelled H2O2 dil. for diluted stock solution of
H2O2, 50 cm3

1

Plastic bottle labelled Cys dil. for diluted stock solution
cysteine.HCl, 50 cm3

1Black plastic test tube, 15 cm 3

1

Capless centrifuge tube, 1.5 cm 3

1

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Plastic beaker, 25 cm3

1

Erlenmeyer flask, 100 cm 3

1

For Problem P3 (in grey basket if not stated otherwise)
Personal equipment
Laboratory stand (bench) with:White sheet of paper
Burette clamp
Burette, 25 cm3Quantity

1 (each)Bulb pipette, 50 cm3 (bench, in pipette stand)1

Bulb pipette, 10 cm3 (bench, in pipette stand)

1

Glass funnel

1

Measuring cylinder, 5 cm3

1

Titration flask (flat bottom flask), 250 cm3

2Erlenmeyer flask, 250 cm 3

1

Fritted glass filter funnel, porosity S1 (blue label)

1

Glass beaker, 100 cm3

2

Glass beaker, 250 cm3

1

Plastic Pasteur pipette, narrow stem, nongraduated2

Plastic Pasteur pipette, thick stem, graduated1

Zipped bag with 5 pH indicator strips and 1 pH scale

1

Zipped bag with 5 absorbing paper strips

1

Waste catex plastic bottle (bench)

1

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Practical
Problem P1

Question

1.1

1.2

yield

m.p.

Total

Points

4

16

20

10

50

14% of the total

Score

Problem P1. Haloform reaction with bleachChemical test reactions have been developed as a means of identifying functional groups inunknown compounds. In this task, you will explore two examples of chemical test reactions on
a preparatory scale, starting from (2-naphthyl)ethanone (A, 2-acetonaphthone):•

The haloform reaction is a transformation typical for methyl ketones which react with basic
aqueous hypohalite solution and provide a carboxylic acid (product B) and a haloform(trihalomethane).

•

The reaction of Brady’s reagent (acidic solution of 2,4-dinitrophenylhydrazine) with thecarbonyl group of an aldehyde or ketone results in the formation of an orange hydrazone
precipitate (product C).

P1.1 Draw the structures of products B and C.

2 points (1 point for 2-naphthoate)

2 points (1 point for intermediate hydrazinealcohol or the product with minor mistake in the
structure – forgotten group or hydrogen atoms inthe side chain)

Product B

Product C

Notes:• The total score will be based on the Rf values of compounds A and B calculated from thesubmitted TLC plate 1 and on the quality and quantity of the submitted products B and C.
• The quality of your products will be graded based on the TLC and melting points.
• The amount of the provided hypochlorite solution is not sufficient to convert all reactant A toproduct B. You will recover the residual reactant A by an acid-base extraction and isolate it after
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the reaction with Brady's reagent as hydrazone C. The grading is based on the combined yield of
products B and C.

Procedure
I. Haloform reaction
1. Turn on the stirrer and adjust the speed to 540 rpm. Immerse a temperature probe, resting thewire on the upper clamp into the bath almost to the bottom and set the temperature to 80 °C.
2. Transfer the 0.500 g of 2-acetonaphthone from the vial labelled Reactant A into a 50 cm3 roundbottom flask that contains a magnetic stir bar. Measure 3 cm3 of ethanol (from the wash bottle) ina measuring cylinder and use it to transfer the remaining reactant A quantitatively into the roundbottom flask using a glass Pasteur pipette.
3. Place the round bottom flask into the hot water bath. Attach an air reflux condenser (water
connection is not needed) and secure it in the upper part by a loosely attached large clamp, asshown in Figure 1. Let compound A dissolve with stirring.

Figure 1. Setup for heating the reaction mixture in a water bath.

4. When the bath temperature reaches 75 °C, slowly add all the NaClO solution (Bleach) to thereaction mixture through the top opening of the condenser using a small glass funnel. Heat thereaction mixture with stirring for 60 minutes between 75 and 80 °C.
5. Then turn off the heating of the hotplate stirrer. Loosen the upper clamp a bit and lift the reaction
flask over the water bath. (Caution! Touch only the clamps, the flask is hot.) Allow the reaction
mixture to cool down for 15 minutes.
II. Workup of the reaction mixture
1. Place a separatory funnel into a metal ring and place a 50 cm3 Erlenmeyer flask without a groundjoint under it. Using a glass funnel, pour the cooled reaction mixture into the separatory funnel.
Remove the stir bar from the glass funnel with tweezers. Measure 5 cm3 of ethyl acetate (EtOAc)
and use it to rinse the reaction flask.. Add the washings into the separatory funnel using a glass
Pasteur pipette.

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2. Perform the extraction. Allow the layers to separate. Collect the aqueous layer into the 50 cm3
Erlenmeyer flask without a ground joint. Using a small glass funnel, pour the organic layer throughthe top neck into the 25 cm3 Erlenmeyer flask. Keep both phases!
3. Using a small funnel, pour the aqueous phase from the 50 cm3 Erlenmeyer flask back to theseparatory funnel. Measure another 5 cm3 of ethyl acetate and repeat the extraction (step No.
II.2). Combine the organic phases together in the 25 cm3 Erlenmeyer flask. Keep both phases!
4. Prepare your TLC plate. Check it before use. Unused damaged plates will be replaced uponrequest without penalty. Use a pencil to draw the start line and mark the positions for spotting thesamples. Write number 1 in a circle and your student code on the top of the TLC plate as shownin Figure 2. Dissolve the given sample of 2-acetonaphthone in a vial (Standard A) in ca. 2 cm3 ofethanol (about 1 full glass Pasteur pipette). Mark three spot positions and label them A, O1, andO2. Spot 1 l (one mark of the 5 l capillary spotter) of standard A and the combined organic
phase from step II.3 (O1). You will add spot O2 later.

Figure 2. Instructions for the TLC plate preparation.

5. Extract the combined organic phases twice with 5 cm3 of 5% Na2CO3 solution. Collect theaqueous phase into the same 50 cm3 Erlenmeyer flask without a ground joint containing theaqueous phase from the first extraction.
6. Wash the organic phase in the funnel with 5 cm3 of deionized water. Add the aqueous phaseto the combined aqueous extracts. Pour the organic layer (O2) through the top neck into a 50
cm3 ground-joint Erlenmeyer flask. Spot 1 l of the solution O2 on your TLC plate preparedin step II.4 (Plate 1).
7. Perform a TLC analysis. Take a 50 cm3 beaker and load it with ca. 2 cm3 of the TLC eluent.
Insert the TLC plate, cover the beaker with a Petri dish and let the eluent reach approximately
0.5 cm bellow the top edge of the plate. Using tweezers, take the TLC plate out, draw theeluent front line and let the plate air-dry. Place the TLC plate under the UV lamp in the hood.
With a pencil, circle all the visualized spots and calculate the Rf values of reactant A andproduct B. Store your TLC plate in a plastic bag.
Note 1: Product B may tail on the TLC plate. Therefore, avoid excessive loading of the sample.

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Note 2: In some cases, two additional spots of side products of a very low intensity may be seenin combined organic phase O1 and O2. In this case, calculate the Rf value for the most intensespot(s).
Note 3: If the organic layer O2 still contains both starting material A and product B, repeat theextraction with the Na2CO3 solution and water (steps No. II.5 and II.6). In this case, submit also
another TLC plate after the repeated extraction (Plate 2), spotting only standard A and organic
phase O2. Mark number 2 in a circle and your student code on the top of this TLC plate. Use a
fresh batch of eluent to develop TLC Plate 2.
P1.2 Answer the following questions about your Plate(s). From Plate 1, calculate the Rf values ofstandard A and product B. Provide the results rounded to 2 decimal places.
Based on the TLC analysis, your organic layer O1 contains:
YES NO
Starting material A
Product B
0.5 point for correct observation about starting material on Plate 1 (in accordance with TLC)
0.5 point for correct observation about product B (in accordance with TLC)

Based on the TLC analysis, your final organic layer O2 contains:
YES NO
Starting material A
Product B
0.5 point for correct observation about starting material on final plate (in accordance withTLC)
0.5 point for correct observation about product B (in accordance with TLC)
Max 2 points for the correct preparation and development of the TLC plate 1:(labelling of the plate with number 1 and student code, start line and eluent front line, initial
position of the spots, labels of the spots, developed spots in circles)−0.5 points for any from the above missing, no negative total points

Calculation of the Rf(A) = distance of the spot from start line/distance between thestart and eluent front lines
Rf(A) = reported by the student
Rf(A)* Rf value calculated by the Scientific Committee (SciC) for the starting material basedon the submitted TLC plate 1
1 point for the calculation of the Rf value
1 point for the agreement with the SciC result:Rf(A)* + 0.02 ≥ Rf(A) ≥ Rf(A)* − 0.02 1 point
Rf(A)* + 0.02 > Rf(A) 0 points
Rf(A)* − 0.02 < Rf(A) 0 points
Master value (MV) = 0.67 (determined from parallel data collected on practical exam day)Max 4 points for the calculated Rf value
MV – 0.07 ≤ Rf(A)* ≤ MV + 0.07
4 points
MV − 0.07 > Rf(A)* > MV – 0.14
Rf (A)* –- (MV –- 0.14)
Number of points = () × 4 points
0.07
MV + 0.07 < Rf(A)* < MV + 0.14

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Number of points = (MV + 0.14– Rf (A)*) × 4 points
0.07

MV + 0.14 ≤ Rf(A)* 0 points
MV – 0.14 ≥ Rf(A)* 0 points

Calculation of the Rf(B) = distance of the spot from start line/distance between thestart and eluent front lines
Rf(B) = reported by the student
Rf(B)* Rf value calculated by the Scientific Committee (SciC) for product B based on thesubmitted TLC plate 1
1 point for the calculation of the Rf value
1 point for the agreement of the student’s and SciC result
Rf(B)* + 0.02 ≥ Rf(B) ≥ Rf(B)* − 0.02 1 point
Rf(B)* + 0.02 > Rf(B) 0 point
Rf(B)* − 0.02 < Rf(B) 0 point
Master value (MV) = 0.12 (determined from parallel data collected on practical exam day)Max 4 points for the calculated Rf value
MV + 0.05 ≥ Rf(B)* ≥ MV – 0.05 4 points
MV – 0.05 > Rf(B)* > MV – 0.10
Number of points =Rf (B)* – (MV – 0.10)
× 4 points
0.05

MV + 0.05 < Rf(B)* < MV + 0.10
Number of points =Rf(B)* ≤ MV + 0.10 0 points
MV – 0.10 ≤ Rf(B)* 0 points

MV + 0.10– Rf (B)*× 4 points
0.05

III. Reaction with Brady’s reagent
Attention: Use gloves! Brady’s reagent stains skin and all surfaces. Wash any spots immediately
with ethanol! Change your gloves if necessary.
Preheat the water bath to 80 °C. Insert a magnetic stir bar into the 50 cm3 ground-joint Erlenmeyer
flask containing the organic phase O2 from step II.6 and add 0.300 g of 2,4-dinitrophenylhydrazine(DNPH). In a graduated cylinder, measure 10 cm3 of ethanol. Using a glass Pasteur pipette, rinse
the glass vial with 5 × 2 cm3 of ethanol to transfer all of the DNPH into the Erlenmeyer flask. Placethe Erlenmeyer flask into the hot water bath, attach a reflux condenser (similar setup as in Figure 1)
rinsed with ethanol. Through the top opening of the condenser, add 3 cm3 of 20% HCl using a funneland stir the reaction mixture at 80 °C for 2 minutes. Fine orange crystals of product C start to form.
Then turn off the heating of the hotplate stirrer. Lift the reaction flask above the water bath. (Caution!
Touch only the clamps, the flask is hot.) Allow the reaction mixture to cool down for 15 min and thenplace it into a cold water bath (prepared by pouring cold tap water in a 150 cm3 beaker).
IV. Isolation of the products
1. Check the pH of the combined aqueous phase from step No. II.6. Acidify it by carefully adding
20% HCl solution, stirring the mixture with a glass rod (ca. 2 cm3 of the HCl solution should be
required), to the final pH of 2 (check with pH indicator strips). A white precipitate of product B isformed.

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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

2. Set up a vacuum filtration apparatus (Figure 3) using a glass fritted funnel with porosity S2 (withwhite label) and secure it to a laboratory stand with a small clamp. Connect the suction flask to
the vacuum source. Pour the suspension of product B (step No. IV.1) into the fritted funnel, let
the solid set down, and then open the vacuum valve. Caution: notify the lab assistant before andafter handling the valve! Wash the solid twice with 6 cm3 of deionized water, until the pH of the
dropping filtrate is about 6. Let air suck through the precipitate for 5 minutes to pre-dry the product.
Disconnect the vacuum source. Use the spatula to transfer white product B to a glass vial labelled
Student code B and leave it uncovered on the bench to dry. Discard the filtrate to the sink drain
and wash the suction flask.
Note: Be careful not to scratch the fritted glass into your product!

Figure 3. Setup for suction filtration.

3. Set up a vacuum filtration apparatus with a glass fritted funnel with porosity S3 (with an orange
label) similarly as in IV.2. Pour the suspension of product C (step No. III) into the fritted funnel,
wait for a minute, and then open the vacuum valve. Do NOT stir or scratch the solid with the
spatula while filtering and washing, otherwise the solid may go through the filter. Wash theprecipitate three times with 5 cm3 of ethanol (15 cm3 in total) until neutral pH of the dropping
filtrate is reached. Let air suck through the precipitate for 5 minutes. Disconnect the vacuum
source. Use the spatula to transfer orange product C to a glass vial labelled Student code C andleave it uncovered on the bench to dry. Collect the filtrate into Organic waste bottle.
Note: If the product goes through the fritted funnel, filter the suspension once more. If the productstill goes through, contact the lab assistant.
Your lab assistant will pick up following items and sign your answer sheet.
• Glass vials labelled Student code B and C with your products• TLC plates in a zipped bag labelled with your Student code
Submitted items:
Product B
Product C

TLC Plate 1

TLC Plate 2 (optional)

Signatures:

PRACTICAL PROBLEMS, OFFICIAL ENGLISH VERSION___________________
Student__________________
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XXX-XINTERNATIONAL CHEMISTRY OLYMPIAD / SLOVAKIA & CZECH REPUBLIC, 2018

Marking notes for evaluation of the yields and product quality
Combined yield of product B and C max 20 points
100% < y (after extended drying will be analyzed by SciC: NMR and insoluble residue).
89.0% ≤ y ≤.100.0%
20 points
y < 89.0% linear dependence:(% C + % B) × 20 points
Number of points =89.0%
Products quality

total max 10 points

Compound B starting point of melting and melting point intervalStarting point of melting of compound B (max 4 points)
m.p.> 186.8 °C Will be evaluated for composition by SciC.
186.8 °C ≥ m.p. ≥ 183.2 °C
4 points
183.2 °C > m.p. > 181.0 °C
m.p.(B) – 181.0 °C
Number of points = 4 × ()
2.2 °Cm.p. ≤ 181.0 °C
0 points
NMR spectrum of the sample will be recorded if the m.p. starts bellow 181.0 °C. Reduction of thepoints for the yield will be applied according to the contents of impurities based on NMR spectra.
Solubility test of the sample will be performed if the sample doesn’t melt completely above 190 °C.
Reduction of the points for the yield will be applied according to the contents of insoluble impurities.
Melting point interval of compound B will be evaluated only if any points were granted for thestarting point of melting (max 4 points)
Interval ≤ 3.1 °C
4 points
3.1 °C < interval < 5.1 °C
5.1 °C – interval
Number of points = 4 × ()
2.0 °CInterval ≥ 5.1 °C
0 points
Purity of compound C (max 2 points)
Qualitative check by the determination of the melting point 240 °C < m.p. < 275 °C. The sample should
not melt below 240 °C (1 point) and no solid residue should remain at 275 °C (1 point).
NMR spectrum of the sample will be recorded if the m.p. starts bellow 240.0 °C. Reduction of thepoints for the yield will be applied according to the contents of impurities based on NMR spectra. If
more than 10% of other compounds than the product are present, 0 points will be given for the yieldof product C.
Solubility test of the sample will be performed if the sample doesn’t melt completely above 275 °C.
Reduction of the points for the yield will be applied according to the contents of impurities based onsolubility test. If more than 10% of insoluble impurity is present, 0 points will be given for the yield of
product C.

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Practical
Problem P2

Question

2.1

2.2

2.3

2.4

2.5

2.6

Total

Points

30

30

7

3

4

6

80

13% of the total

Score

Problem P2. A glowing clock reaction
Luminol is a well-known source of chemiluminescence. In the presence of a suitable redox catalyst,
e.g. Cu2+, it may react with oxidizing agents, most commonly H2O2, forming products in excitedelectronic states. These release the excess energy by the emission of blue light:

The procedure may be modified into a clock reaction, in which the light appears after a certain
induction time. By adding cysteine, Cu(II) is reduced to Cu(I) and captured in a Cu(I)–cysteinecomplex that does not facilitate the luminol oxidation. However, the inhibition is only temporary.
A cycle of reactions fuelled by H2O2 leads to the gradual oxidation of cysteine:

Eventually, all cysteine is consumed, Cu(I) is reoxidized to Cu(II), and its catalytic activity is restored.
This is indicated by a flash of blue chemiluminescence. The time it takes for the flash to appear canbe used to study the rates of the Cu-catalyzed cysteine oxidation.

Procedure
Caution: Always keep all your solutions and pipettes away from hotplates!
Reasonable temperature changes are not a problem, because your results will be marked based on
the actual reaction temperatures that you report. You will not lose any points if your data is recorded
at various temperatures. However, you must avoid excessive heat, e.g. placing the solutions or the
pipettes near a hotplate.
Note: Report all the values with the requested number of significant figures or decimal places.
Excessive rounding may make it impossible to distinguish a correct answer from an incorrect one.
General structure of the experiment
In Part I, you will dilute two stock solutions that are provided as concentrates. In Part II, you willmeasure the reaction times of the clock reaction for two different concentration sets, as defined in
the table below:
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Volume in the black test tube

In the centrifuge tube

Water

Luminol in NaOH

Cys dil.

Cu

H2O2 dil.

Conc. set #1

3.00 cm3

2.50 cm33.30 cm3

0.50 cm3

0.70 cm3

Conc. set #2

3.30 cm3

2.50 cm33.30 cm3

0.50 cm3

0.40 cm3

It is recommended that before you start measuring the data to be graded, you should get familiar
with the procedure in a trial run.
Because the reaction rate depends on temperature, you must record the actual temperatures in all
replicates. The temperatures in the reaction mixtures should be measured IMMEDIATELY AFTER
you have recorded the reaction time required to produce the blue flash.
In data evaluation, each temperature recorded from the thermometer’s display must be corrected bysumming it with the thermometer’s calibration constant. This constant is printed on a piece of paperin the basket for Problem 2.
Then, each reaction time t(x °C) observed at x °C (corrected) must be converted to the time t(25 °C)
that would be observed at 25 °C. This normalization of reaction times to 25 °C is a simple
multiplication of t(x °C) with a normalization coefficient nx→25:t(25 °C) = nx→25 t(x °C)
The values of the normalization coefficients nx→25 corresponding to various temperatures are listed
in Table P2 at the end of this task.
I. Dilution of the concentrated stock solutions
Solutions of H2O2 (2.00 mol dm−3) and cysteine (0.100 mol dm−3) are provided as concentrates,labelled H2O2 conc. and Cys conc. Using the 5 cm3 bulb pipette and the 50 cm3 volumetric flask,
dilute 5.00 cm3 of each to 50.00 cm3 with deionized water and store the diluted solution in the bottles
labelled H2O2 dil. and Cys dil.
For measuring the solution volumes in the following steps, assign one graduated pipette for each of
the bottles. The 5 cm3 pipettes are for Luminol in NaOH, Cys dil., and Water. The 1 cm3 pipettes
are for Cu (2.00 mmol dm−3) and H2O2 dil.
II. The clock reaction procedure
Note: Read the entire Section II carefully before starting the experiment.
1. Place the black test tube inside the Erlenmeyer flask serving as a stand. Using the assigned
pipettes, charge the test tube with the prescribed volumes of Water, Luminol in NaOH and
Cys dil. solution.
2. Place the small centrifuge tube inside the small plastic beaker and charge it with the prescribedvolumes of Cu solution and H2O2 dil. solution.
3. Without delay, insert the small centrifuge tube inside the black test tube – gently, without
mixing the two solutions!

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4. Close the test tube with its screw-on cap. Make sure that the tube is closed tightly, because you
will be shaking it. Caution: Do not force the cap beyond its end-point, because the tube will
start leaking. If this happens, you must ask for a replacement immediately (penalty rules apply).
5. Have the stopwatch ready in your hand, in timing mode. The moment you begin shaking the test
tube, start timing. You must shake vigorously during the initial 10 seconds, so that the twosolutions mix perfectly. It is crucial that you do not cut down the shaking time.
6. Return the test tube into the Erlenmeyer flask, open the lid and watch the solution inside closely.
It may help to shield away the daylight with your hand. Eventually, you will see a flash of blue lightthrough the whole solution. At that moment, stop timing.
7. Immediately, insert the metal probe of the digital thermometer into the black test tube. Wait for
the reading to stabilize (typically 10–30 s) and record the reaction time and the reaction
temperature.
8. Using tweezers, remove the small centrifuge tube from the black test tube. After each experiment,
empty and wash both tubes and dry them with paper wipes.

Measured data and their evaluation
P2.1 In the following table, record your experimental results for concentration set #1. To thedisplayed temperature add the thermometer’s calibration constant. Look up the value of thenormalization coefficient nx→25 for each temperature in Table P2 and calculate the reaction
times normalized to 25 °C. In an unlikely case that your temperatures are not listed in Table
P2, get the value of nx→25 from the lab assistant.
Note: Just as the tolerance for correct values in titration is ±0.1 cm3, the tolerance for correct valuesof the normalized times in the concentration set #1 is ±2.3 s.
(Use as many replicates as you consider necessary, you do not need to fill in all the rows.
Points will be awarded for the accepted value only.)

ReplicateConc.
set #1

Reaction time[s]

Displayed
temperature[°C]

Corrected
temperature[°C]

Reaction timenormalized to 25 °C[s]

1 decimalplace

1 decimalplace

3 significant figures

1 decimal
place

1

57.1

27.5

27.4

68.3

2

56.0

27.7

27.6

68.0

3

55.7

27.8

27.7

68.2

Accepted value of the normalized reaction time
for concentration set #1

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P2.2 In the following table, record your experimental results, the corrected temperature andcalculate the reaction times normalized to 25 °C for concentration set #2.
Note: Just as the tolerance for correct values in titration is ±0.1 cm3, the tolerance for the correct
values of the normalized times in the concentration set #2 is ±3.0 s.
(Use as many replicates as you consider necessary; you do not need to fill in all the rows.
Points will be awarded for the accepted value only.)

ReplicateConc.
set #2

Reaction time[s]

Displayed
temperature[°C]

Corrected
temperature[°C]

Reaction timenormalized to 25 °C[s]

1 decimalplace

1 decimalplace

3 significant figures

1 decimal
place

1

71.9

27.9

27.8

86.6

2

70.6

27.9

27.8

85.1

3

72.5

27.8

27.7

86.8

Accepted value of the normalized reaction time
for concentration set #2
P2.3

86.2

Based on the procedure and on the concentrations of the stock solutions (specified in the listof chemicals and in Part I. of the Procedure), calculate the initial concentrations of cysteine,
copper and H2O2 in both concentration sets.
Express the accepted reaction times (t1 and t2) from P2.1 and P2.2 in minutes and calculate
the corresponding reaction rates (v1 and v2), expressed as the rates of the consumption of
the cysteine concentration, in mmol dm−3 min−1. You can assume that the rate of cysteine
consumption during the reaction is constant.
If you cannot find the reaction rates, use the value 11.50 for conc. set #1 and 5.500 for conc.
set #2 in further calculations.
Initial concentrations[mmol dm−3]
3 significant figures
Cysteine

Copper[Cu]

Conc. set #1
3.30

Acceptedreaction time[min]

Reaction rate
[mmol dm−3 min−1]
4 significant figures

H2O2

4 significant
figures

14.0

1.137

2.902

8.00

1.437

2.296

0.100

Conc. set #2

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P2.4

Assuming the rate equation can be expressed asv = k [H2 O2 ]p
use your experimental data to calculate the partial reaction order p with respect to H2O2. Write
down your answer with 2 decimal places and show your calculation.
Answer:p = 0.42

Calculation:p2.902 mmol dm–3 min–1 = k (14.0 mmol dm–3 )p2.296 mmol dm–3 min–1 = k (8.00 mmol dm–3 )
2.902
14.0 p
= (
)
2.296
8.00
p=

log 1.264
log 1.75

An expression of the rate law of cysteine consumption that is closer to reality is more
complicated and takes the following form:v = k1 [H2 O2 ][Cu] + k2 [Cu]P2.5

Using the data from P2.3, evaluate the dependence of v on [H2O2] as a linear function to findthe slope and the intercept. Write down both answers with 4 significant figures. If you cannot
find constants a and b, use the value 11.50 for both a and b in further calculations.
Answers (do not include the calculation, but include units):v = a[H2 O2 ] + b

P2.6

a = 0.1010 min−1

b = 1.488 mmol dm−3 min−1

Use the numeric values from P2.5 to evaluate the rate constants k1 and k2. Write down theirvalues with 3 significant figures.
Answers (including units):
k1 = 1.01 min−1 mmol−1 dm3

k2 = 14.9 min−1

Calculations:k1 [Cu] = a  k1 = a / [Cu] = 0.1010 min−1 / (0.100 mmol dm−3)
k2 [Cu] = b  k2 = b / [Cu] = 1.488 mmol dm−3 min−1 / (0.100 mmol dm−3)

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Marking notes
Incorrect number of significant figures and decimal places will not be penalized.
P2.1

Maximum 30 points, evaluated as follows:
1) The reported reaction temperature is combined with the individual calibration constant of thethermometer to find the correct temperature. The correct temperature is used to normalize thereported reaction time to a value that would be measured at 25 °C, according to Table P2. This isfor informative feedback on the contestant’s raw data, or to be used if the Accepted Value wasbased on incorrect normalization – see point 4).
2) The interval of Accepted Values deserving full marks (30 points) is the interval of answers collected
when the procedure is performed correctly:
Master Value (determined in parallel experiments during the exam): 67.7 s.
The width of the full-marks interval (determined from a sample of 95 results from students trained
to perform the procedure correctly): MV ±3.5% (±2.4 s).
3) Values not totally correct should receive less than full marks. The number of points received for an
incorrect answer decreases linearly with the distance from the interval delineating correct answers.
The minimum of 0 points is for unacceptably incorrect values, i.e. beyond MV ±7.0% (±4.8 s).
4) If contestant’s calculation of the corrected temperature and of the normalized reaction time is
missing or involves errors, a substitute Accepted Value is taken for grading. This is based on thecorrectly normalized reaction times calculated from contestant’s raw data - see point 1), following
the contestant’s choice of Accepted Value or taking the mean if the choice cannot be identified.

P2.2

Maximum 30 points, evaluated as in P2.1:
Master Value (determined in parallel experiments during the exam): 88.9 s.
Full marks (determined as for P2.1): within MV ±3.5% (±3.1 s)
0 points: beyond MV ±7.0% (±6.2 s)

P2.3

Maximum 7 points total:
1 point for each correct concentration, 0 points for incorrect answers
0.5 point for each correct conversion of a reaction time to minutes, 0 points for incorrect answers
1 point for each correct calculation of the rate of cysteine consumption, 0 points for incorrect answers

P2.4

Maximum 3 points total:
2 points for correct calculation (showing at least one formula that can be evaluated to yield the result)
1 point for correct value of the result

P2.5

Maximum 4 points total:
2 points for each correctly calculated parameter including correct unit, 1 point for each correct
numerical value with incorrect or no unit, 1 point for each incorrect numeric value including correct
unit, 0 points for each incorrect value with incorrect or no unit

P2.6

Maximum 6 points total:
2 points for correct calculation (showing the formulas that can be evaluated to yield the results)
2 points for each correct rate constant including correct units, 1 point for each correct numeric value
with incorrect or no unit, 1 point for each incorrect numeric value including correct unit, 0 points foreach incorrect value with incorrect or no unit.

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Table P2. Normalization coefficients nx→25 for converting reaction times measured at various temperatures
to times representing the reactions at 25.0 °C.

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Practical
Problem 3
13% of the total

Question

3.1

3.2

3.3

3.4

3.5

Points

3

20

2

2

16

Question

3.6

3.7

3.8

3.9

3.10

Total

Points

4

20

2

4

2

75

Score

Score

Problem P3. Mineral water identification
Many mineral and thermal water springs are registered in Slovakia. Mineral waters with a balanced
composition and natural or modified carbon dioxide content are sold for daily consumption. Thesewaters do not contain nitrites, nitrates, phosphates, fluorides and sulfides and are also free of ironand manganese.
The mass concentration of the most important ions is reported on the packaging.
Your task is to identify the trade brand (from Table P3.1) of your mineral water sample.
Note: CO2 has been removed from the sample.
Table P3.1. Mass concentrations of ions in selected Slovak mineral waters. (As reported by the supplier.)
Mass concentration of ion, mg dm−3No.

Trade brand

1

Ca2+

Mg2+

Na+

K+

Cl−

SO42−

HCO3−

Kláštorná

290

74

71

16

15

89

1 341

2

Budišská

200

50

445

50

25

433

1 535

3

Baldovská

378

94

90

0

78

215

1 557

4

Santovka

215

67

380

45

177

250

1 462

5

Slatina

100

45

166

40

104

168

653

6

Fatra

45

48

550

16

36

111

1 693

7

Ľubovnianka

152

173

174

5

10

20

1 739

8

Gemerka

376

115

85

0

30

257

1 532

9

Salvator

473

161

214

30

116

124

2 585

10

Brusnianka

305

101

187

35

59

774

884

11

Maxia

436

136

107

18

37

379

1 715

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Notes:• Use the prescribed symbols in the notations of calculations.
• You are provided with a swollen cation exchange resin (Catex) in its H+ form. Use a thick stem
Pasteur pipette for transferring it. You can add more deionized water to the resin if necessary (itshould not dry out).
• Concentrations of the standard solutions:c(NaOH) = 0.2660 mol dm−3c(EDTA) = 5.965 × 10−3 mol dm−3

Procedure
1.a Measure 5.00 cm3 of the catex into the graduated cylinder (volume
V1). Then using deionized water transfer the catex quantitatively intoa titration flask. Add an appropriate amount of deionized water so thatthe suspension can be swirled well and the colour of the solution overthe catex can be observed.
1.b Add 3–4 drops of the bromothymol blue indicator (BTB) and about
1 g (half a spoon) of solid NaCl. When NaCl dissolves, titrate all thesuspension with the standard sodium hydroxide solution (volume V2)
from yellow to blue. Close to the equivalence point, titrate slowly andswirl well so that any analyte inside the catex skeleton may diffuse
into the solution. Repeat the experiment as necessary.

← Catex level (5.00 cm3)

1.c After the titration, decant and discard most of the aqueous solution
in the titration flask above the catex and transfer the suspension to the Waste catex container.
P3.1 Write down all the chemical reactions which occur in Step 1. Use R–H as a formula for thecatex in a H+ form and HInd for the indicator.
Ion exchange
R–H + NaCl ⇆ R–Na + HCl
1 point for the correct equation

Neutralization
HCl + NaOH ⇆ NaCl + H2 O
1 point for the correct equation

Indication
HInd + OH– ⇆ Ind– + H2 O
1 point for the correct equation

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P3.2 Enter the experimental and accepted values from Step 1 into the table.
(You do not need to fill in all the rows.)

AnalysisNo.

Catex volume

NaOH consumption

V1 [cm3]

V2 [cm3]

1

e.g. 19.00

2

5.00

3

e.g. 19.50
e.g. 19.70

Accepted value V2
4 significant figurese.g. 19.40

Maximum 20 points based on the agreement between the master and accepted values V2 (specified in Marking
notes; the number of replications is not evaluated).

P3.3 Using the accepted value of V2, calculate the ion exchange volume capacity Qv(H+) in
mmol cm−3.
Calculation:
V2 × c(NaOH) 19.40 cm3 × 0.2660 mol dm–3
Qv (H ) === 1.032 mmol cm–3
V1
5.0 cm3+

1 point for the correct calculation procedure
1 point for correct result

If you cannot find the Qv(H+) value, use 1.40 mmol cm−3 for further calculations.
2.a Using a graduated cylinder, measure 5.00 cm3 of the swollen catex (volume V3). Transfer themeasured catex quantitatively into the 250 cm3 beaker. Using a pipette, add 50.00 cm3 of yoursample (volume V4). Swirl the mixture occasionally for about 5 minutes. Use the Erlenmeyer flask
as a stand for the funnel and to collect the filtrate. Then filter the catex through a fritted funnel(porosity S1) and wash it with deionized water to a neutral pH (check with pH paper). Discard thefiltrate.
2.b Using deionized water, transfer the catex quantitatively from the funnel into a titration flask anddiscard the filtrate.
2.c Add 3–4 drops of bromothymol blue indicator and about 1 g (half a spoon) of solid NaCl andtitrate the suspension with the standard sodium hydroxide solution (volume V5) from yellow toblue. Repeat the experiment as necessary.
2.d After the titration, decant and discard most of the aqueous solution in the titration flask above
the catex and transfer the suspension to the Waste catex container.

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P3.4 Write down the equations for the ion exchange reactions. Monovalent and divalent ions shouldbe abbreviated M+ and M2+, respectively.
Ion exchange from the sample
R–H + M+ ⇆ R–M + H+
2 R–H + M2+ ⇆ R2 –M + 2 H+
2 points – 1 point for each correct equation or 2 points for the correct general equation with Mn+

P3.5 Enter the experimental and accepted values from Step 2 into the table.
(You do not need to fill in all the rows.)
Catex
volumeV3 [cm3]

Analysis
No.

Sample volume
V4 [cm3]

1

NaOH
consumption
V5 [cm3]
e.g. 13.00

2

5.00

50.00

3

e.g. 13.20
e.g. 13.10

Accepted value V5
4 significant figurese.g. 13.10

Maximum 16 points based on the agreement between the master and accepted values V5 (specified in Marking
notes; the number of replications is not evaluated).

P3.6 Consider that all the ions in your solution are M+ ions. For the accepted value of V5, calculate
the total amount of cations (as M+ molar concentration) in 1 dm3 of mineral water. Show thecalculation of the total equivalent concentration of cations, c*(M+) in mmol dm−3.
Calculation:*+c (M ) =c* (M+ ) =V3 × Qv (H+ )ionex – V5 × c(NaOH)
V4
5.00 cm3 × 1.032 mol dm–3 – 13.10 cm3 × 0.2660 mol dm–3
50.00 cm3

c* (M+ ) = 33.51 mmol dm–3
3 points for the correct calculation procedure
1 point for correct result including unit

If you cannot find the c*(M+) value, use 35.00 mmol dm−3 for further procedure.
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In the next step, you are going to perform complexometric analysis to determine the concentrationof Ca2+ and Mg2+ together (hereinafter written as M2+).
3. Pipette 10.00 cm3 (V6) of the sample into the titration flask and add ca. 25 cm3 of deionized water.
Adjust pH by adding 3 cm3 of the buffer solution. Add some Eriochrome black T indicator (EBT,on the tip of the spatula) and titrate with the standard EDTA solution from wine red to blue (V7).
P3.7 Enter the experimental and accepted values from Step 3 into the table.
(You do not need to fill in all the rows)

Analysis

Sample volume

EDTA consumption,No.

V6 [cm3]

V7 [cm3]

1

e.g. 14.20

2

10.00

3

e.g. 14.25
e.g. 14.25

Accepted value V7
4 significant figurese.g. 14.25

Maximum 20 points based on the agreement between the master and accepted values V7 (specified in Marking
notes; the number of replications is not evaluated).

P3.8 For the accepted volume of V7, calculate the molar concentration of M2+ cations in mineralwater, c(M2+) in mmol dm−3.
Calculation:c(M2+ ) =V7 × c(EDTA)
V6

c(M2+ ) =14.25 cm3 × 5.965 mmol dm–3
= 8.500 mmol dm–3
10.00 cm3

1 point for the correct calculation procedure
1 point for correct result including unit

If you cannot find the c(M2+) value, use 15.00 mmol dm−3 for further solution.
4. Use Table P3.2 in next identification procedure.
P3.9 In Table P3.2, write down experimentally found values from tasks P3.6 and P3.8 and tick (✓)
all the lines with approximate match (±10%) of the found parameter c(M2+) and c*(M+) with thedata from the label.

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Table P3.2
Mineral water

Supplier datac(M2+)
No.

Trade brand

c(M+)
−3

−3

[mmol dm ] [mmol dm ]Match with the experimentTotal
equivalentconcentrationof cations
c*(M+)[mmol dm−3]

Conformity
for c(M2+)

Conformity
for c*(M+)

XXX

XXX

Your exp. values

8.50

XXX

33.51

1

Kláštorná

10.30

3.50

24.1

2

Budišská

7.06

20.63

34.7

✓

3

Baldovská

13.32

3.91

30.5

✓

4

Santovka

8.13

17.67

33.9

5

Slatina

4.35

8.25

16.9

6

Fatra

3.11

24.32

30.5

7

Ľubovnianka

10.92

7.70

29.5

8

Gemerka

14.13

3.70

32.0

9

Salvator

18.46

10.07

47.0

10

Brusnianka

11.79

9.03

32.6

11

Maxia

16.50

5.11

38.1

✓

✓

✓

✓

✓

Maximum 4 points. For each column: 2 points if correctly marked, 1 point if partially marked.

P3.10 Based on your results, decide which mineral water is in your sample. Tick (✓) the crossreference number(s) of the mineral water(s).
No.

Trade brandNo.

Trade brand1

Kláštorná

7Ľubovnianka

2

Budišská8

Gemerka

3

Baldovská

9

Salvator

Santovka

10

Brusnianka

5

Slatina

11

Maxia

6

Fatra

12

other

4

✓

2 points if consistent with the results marked in Table 3.2 (Kláštorná or Ľubovnianka, if values from P3.6 andP3.8 are accurate)
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Marking notes
P3.2

Full points if relative deviation is lower than ±1.5% of the master value.
Acquired points are calculated from the following equation:
Score = 32.0 – 8.0 × |(V2student – V2master) / V2master| × 100,0 points if relative deviation is higher than ±4.0% of the master value.
V2master = 13.10, 17.20, or 20.65 cm3

P3.5

Full points if relative deviation is lower than ±4.0% of the master value.
Acquired points are calculated from the following equation:
Score = 21.81818 – 1.45455 × |(V5student – V5master) / V5master| × 100,0 points if relative deviation is higher than ±15.0% of the master value.
V5master = from 7.54 to 16.12 cm3

P3.7

Full points if relative deviation is lower than ±0.5% of the master value.
Acquired points are calculated from the following equation:
Score = 25.0 – 10.0 × |(V7student – V7master) / V7master| × 100,0 points if relative deviation is higher than ±2.5% of the master value.
V7master = 17.15 or 18.41 cm3

Replaced chemicals and equipment
Signature
Item or incident

Penalty
Student

Lab assistant

0 pt

PRACTICAL PROBLEMS, OFFICIAL ENGLISH VERSION

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