Uploaded by Semwezi Enock

10.1

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10.1 [134 marks]
1. [1 mark]
Iron is a stronger reducing agent than silver.
What is correct when this voltaic cell is in operation?
Markscheme
D
2. [1 mark]
What is correct in an electrolytic cell?
Markscheme
D
3. [1 mark]
Which functional groups are present in this molecule?
A. carbonyl, ether, nitrile
B. carbonyl, ester, nitrile
C. carboxyl, ether, amine
D. carboxyl, ester, amine
Markscheme
A
4. [1 mark]
What is the IUPAC name of this molecule?
A. 1,1,2,4-tetramethylpent-1-ene
B. 2,4,5-trimethylhex-4-ene
C. 2,4,5,5-tetramethylpent-4-ene
D. 2,3,5-trimethylhex-2-ene
Markscheme
D
5. [1 mark]
Which compound with the molecular formula 𝐢4 𝐻8 𝑂 has this high resolution H1 NMR?
From: libretexts.org. Courtesy of Chris Schaller, Professor (Chemistry)
at College of Saint Benedict/Saint John’s University.
A. but-3-en-2-ol, 𝐢𝐻2 = 𝐢𝐻𝐢𝐻(𝑂𝐻)𝐢𝐻3
B. butanal, 𝐢𝐻3 𝐢𝐻2 𝐢𝐻2 𝐢𝐻𝑂
C. butanone, 𝐢𝐻3 𝐢𝑂𝐢𝐻2 𝐢𝐻3
D. but-3-en-1-ol, 𝐢𝐻2 = 𝐢𝐻𝐢𝐻2 𝐢𝐻2 𝑂𝐻
Markscheme
B
6a. [2 marks]
Compound A is in equilibrium with compound B.
Predict the electron domain and molecular geometries around the oxygen atom of molecule A
using VSEPR.
Markscheme
Electron domain geometry: tetrahedral βœ”
Molecular geometry: bent/V-shaped βœ”
6b. [1 mark]
The IR spectrum of one of the compounds is shown:
COBLENTZ SOCIETY. Collection © 2018 copyright by the U.S. Secretary of Commerce on behalf of
the United States of America. All rights reserved.
Deduce, giving a reason, the compound producing this spectrum.
Markscheme
B AND 𝐢 = 𝑂 absorption/1750 << π‘π‘š−1 >>
OR
B AND absence of 𝑂𝐻 /3200 − 3600 << π‘π‘š−1 π‘Žπ‘π‘ π‘œπ‘Ÿπ‘π‘‘π‘–π‘œπ‘› >> βœ”
Accept any value between 1700 − 1750 π‘π‘š−1 .
6c. [2 marks]
Compound A and B are isomers. Draw two other structural isomers with the formula 𝐢3 𝐻6 𝑂.
Markscheme
Accept any two 𝐢3 𝐻6 𝑂 isomers except for propanone and propen-2-ol:
βœ”βœ”
Penalize missing hydrogens in displayed structural formulas once only.
6d. [1 mark]
The equilibrium constant, 𝐾𝑐 , for the conversion of A to B is 1.0 × 108 in water at 298𝐾.
Deduce, giving a reason, which compound, A or B, is present in greater concentration when
equilibrium is reached.
Markscheme
𝐡 AND 𝐾𝑐 is greater than 1/large βœ”
7a. [1 mark]
Nickel catalyses the conversion of propanone to propan-2-ol.
Outline how a catalyst increases the rate of reaction.
Markscheme
provides an alternative pathway/mechanism AND lower πΈπ‘Ž βœ”
Accept description of how catalyst lowers πΈπ‘Ž (e.g. “reactants adsorb on surface «of catalyst»”,
“reactant bonds weaken «when adsorbed»”).
7b. [2 marks]
Explain why an increase in temperature increases the rate of reaction.
Markscheme
more/greater proportion of molecules with 𝐸 ≥ πΈπ‘Ž βœ”
greater frequency/probability/chance of collisions «between the molecules»
OR
more collision per unit of time/second βœ”
7c. [3 marks]
Discuss, referring to intermolecular forces present, the relative volatility of propanone and
propan-2-ol.
Markscheme
hydrogen bonding/bonds «and dipole–dipole and London/dispersion forces are present in»
propan-2-ol βœ”
dipole–dipole «and London/dispersion are present in» propanone βœ”
propan-2-ol less volatile AND hydrogen bonding/bonds stronger «than dipole–dipole »
OR
propan-2-ol less volatile AND «sum of all» intermolecular forces stronger βœ”
7d. [1 mark]
The diagram shows an unlabelled voltaic cell for the reaction
𝑃𝑏 2+ (π‘Žπ‘ž) + 𝑁𝑖(𝑠) → 𝑁𝑖 2+ (π‘Žπ‘ž) + 𝑃𝑏(𝑠)
Label the diagram with the species in the equation.
Markscheme
7e. [1 mark]
Suggest a metal that could replace nickel in a new half-cell and reverse the electron flow. Use
section 25 of the data booklet.
Markscheme
𝐡𝑖/𝐢𝑒/𝐴𝑔/𝑃𝑑/𝐻𝑔/𝑃𝑑/𝐴𝑒 βœ”
Accept 𝑆𝑏 OR 𝐴𝑠.
7f. [2 marks]
Describe the bonding in metals.
Markscheme
electrostatic attraction βœ”
between «a lattice of» metal/positive ions/cations AND «a sea of» delocalized electrons βœ”
Accept “mobile/free electrons”.
7g. [1 mark]
Nickel alloys are used in aircraft gas turbines. Suggest a physical property altered by the
addition of another metal to nickel.
Markscheme
Any of:
malleability/hardness
OR
«tensile» strength/ductility
OR
density
OR
thermal/electrical conductivity
OR
melting point
OR
thermal expansion βœ”
Do not accept corrosion/reactivity or any chemical property.
Accept other specific physical properties.
8a. [1 mark]
Chlorine undergoes many reactions.
State the full electron configuration of the chlorine atom.
Markscheme
1𝑠 2 2𝑠 2 2𝑝6 3𝑠 2 3𝑝5 βœ”
Do not accept condensed electron configuration.
8b. [1 mark]
State, giving a reason, whether the chlorine atom or the chloride ion has a larger radius.
Markscheme
𝐢𝑙 − AND more «electron–electron» repulsion βœ”
Accept 𝐢𝑙 − AND has an extra electron.
8c. [2 marks]
Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.
Markscheme
𝐢𝑙 has a greater nuclear charge/number of protons/𝑍𝑒𝑓𝑓 «causing a stronger pull on the outer
electrons» βœ”
same number of shells
OR
same «outer» energy level
OR
similar shielding βœ”
8d. [1 mark]
The mass spectrum of chlorine is shown.
NIST Mass Spectrometry Data Center Collection © 2014 copyright by the U.S. Secretary of
Commerce on behalf of the United States of America. All rights reserved.
Outline the reason for the two peaks at π‘š/𝑧 = 35 and 37.
Markscheme
«two major» isotopes «of atomic mass 35 and 37» βœ”
8e. [2 marks]
Explain the presence and relative abundance of the peak at π‘š/𝑧 = 74.
Markscheme
«diatomic» molecule composed of «two» chlorine-37 atoms βœ”
chlorine-37 is the least abundant «isotope»
OR
low probability of two Cl37 «isotopes» occurring in a molecule βœ”
8f. [1 mark]
2.67𝑔 of manganese(IV) oxide was added to 200.0π‘π‘š3 of 2.00π‘šπ‘œπ‘™π‘‘π‘š−3 𝐻𝐢𝑙.
𝑀𝑛𝑂2 (𝑠) + 4𝐻𝐢𝑙(π‘Žπ‘ž) → 𝐢𝑙2 (𝑔) + 2𝐻2 𝑂(𝑙) + 𝑀𝑛𝐢𝑙2 (π‘Žπ‘ž)
Calculate the amount, in π‘šπ‘œπ‘™, of manganese(IV) oxide added.
Markscheme
2.67𝑔
<< 86.94π‘”π‘šπ‘œπ‘™−1 =>> 0.0307 << π‘šπ‘œπ‘™ >> βœ”
8g. [2 marks]
Determine the limiting reactant, showing your calculations.
Markscheme
<< 𝑛𝐻𝐢𝑙 = 2.00π‘šπ‘œπ‘™π‘‘π‘š−3 × 0.2000π‘‘π‘š3 >>= 0.400π‘šπ‘œπ‘™ βœ”
<<
0.400
4
=>> 0.100π‘šπ‘œπ‘™ AND 𝑀𝑛𝑂2 is the limiting reactant βœ”
Accept other valid methods of determining the limiting reactant in M2.
8h. [1 mark]
Determine the excess amount, in π‘šπ‘œπ‘™, of the other reactant.
Markscheme
<< 0.0307π‘šπ‘œπ‘™ × 4 = 0.123π‘šπ‘œπ‘™ >>
<< 0.400π‘šπ‘œπ‘™0.123π‘šπ‘œπ‘™ =>> 0.277 << π‘šπ‘œπ‘™ >> βœ”
8i. [1 mark]
Calculate the volume of chlorine, in π‘‘π‘š3 , produced if the reaction is conducted at standard
temperature and pressure (STP). Use section 2 of the data booklet.
Markscheme
<< 0.0307π‘šπ‘œπ‘™ × 22.7π‘‘π‘š3 π‘šπ‘œπ‘™ −1 =>> 0.697 << π‘‘π‘š3 >> βœ”
Accept methods employing 𝑝𝑉 = 𝑛𝑅𝑇.
8j. [2 marks]
State the oxidation state of manganese in 𝑀𝑛𝑂2 and 𝑀𝑛𝐢𝑙2 .
Markscheme
𝑀𝑛𝑂2 : +4 βœ”
𝑀𝑛𝐢𝑙2 : +2 βœ”
8k. [1 mark]
Deduce, referring to oxidation states, whether 𝑀𝑛𝑂2 is an oxidizing or reducing agent.
Markscheme
oxidizing agent AND oxidation state of 𝑀𝑛 changes from +4 to +2/decreases βœ”
8l. [1 mark]
Chlorine gas reacts with water to produce hypochlorous acid and hydrochloric acid.
𝐢𝑙2 (𝑔) + 𝐻2 𝑂(𝑙) β‡Œ 𝐻𝐢𝑙𝑂(π‘Žπ‘ž) + 𝐻𝐢𝑙(π‘Žπ‘ž)
Hypochlorous acid is considered a weak acid. Outline what is meant by the term weak acid.
Markscheme
partially dissociates/ionizes «in water» βœ”
8m. [1 mark]
State the formula of the conjugate base of hypochlorous acid.
Markscheme
𝐢𝑙𝑂− βœ”
8n. [1 mark]
Calculate the concentration of 𝐻 + (π‘Žπ‘ž) in a 𝐻𝐢𝑙𝑂(π‘Žπ‘ž) solution with a 𝑝𝐻 = 3.61.
Markscheme
<< [𝐻 + ] = 10−3.61 =>> 2.5 × 10−4 << π‘šπ‘œπ‘™π‘‘π‘š−3 >> βœ”
8o. [1 mark]
State the type of reaction occurring when ethane reacts with chlorine to produce
chloroethane.
Markscheme
«free radical» substitution/𝑆𝑅 βœ”
Do not accept electrophilic or nucleophilic substitution.
8p. [1 mark]
Predict, giving a reason, whether ethane or chloroethane is more reactive.
Markscheme
chloroethane AND C–Cl bond is weaker/324π‘˜π½π‘šπ‘œπ‘™ −1 than C–H bond/414π‘˜π½π‘šπ‘œπ‘™ −1
OR
chloroethane AND contains a polar bond βœ”
Accept “chloroethane AND polar”.
8q. [3 marks]
Explain the mechanism of the reaction between chloroethane and aqueous sodium hydroxide,
π‘π‘Žπ‘‚π»(π‘Žπ‘ž), using curly arrows to represent the movement of electron pairs.
Markscheme
curly arrow going from lone pair/negative charge on 𝑂 in −OH to 𝐢 βœ”
curly arrow showing 𝐢𝑙 leaving βœ”
representation of transition state showing negative charge, square brackets and partial bonds
βœ”
Accept 𝑂𝐻 − with or without the lone pair.
Do not accept curly arrows originating on 𝐻 in 𝑂𝐻 − .
Accept curly arrows in the transition state.
Do not penalize if 𝐻𝑂 and 𝐢𝑙 are not at 180°.
Do not award M3 if 𝑂𝐻 − 𝐢 bond is represented.
8r. [1 mark]
Ethoxyethane (diethyl ether) can be used as a solvent for this conversion.
Draw the structural formula of ethoxyethane
Markscheme
/ 𝐢𝐻3 𝐢𝐻2 𝑂𝐢𝐻2 𝐢𝐻3 βœ”
Accept (𝐢𝐻3 𝐢𝐻2 )2 𝑂.
8s. [3 marks]
Deduce the number of signals and chemical shifts with splitting patterns in the 1H
NMR spectrum of ethoxyethane. Use section 27 of the data booklet.
Markscheme
2 «signals» βœ”
0.9−1.0 AND triplet βœ”
3.3−3.7 AND quartet βœ”
Accept any values in the ranges.
Award [1] for two correct chemical shifts or two correct splitting patterns.
8t. [2 marks]
𝐢𝐢𝑙2 𝐹2 is a common chlorofluorocarbon, 𝐢𝐹𝐢.
Calculate the percentage by mass of chlorine in 𝐢𝐢𝑙2 𝐹2.
Markscheme
<< 𝑀(𝐢𝐢𝑙2 𝐹2 ) =>> 120.91 << π‘”π‘šπ‘œπ‘™ −1 >> βœ”
2×35.45π‘”π‘šπ‘œπ‘™−1
120.91π‘”π‘šπ‘œπ‘™−1
× 100% =>> 58.64 << % >> βœ”
Award [2] for correct final answer.
8u. [1 mark]
Comment on how international cooperation has contributed to the lowering of 𝐢𝐹𝐢 emissions
responsible for ozone depletion.
Markscheme
Any of:
research «collaboration» for alternative technologies «to replace 𝐢𝐹𝐢s»
OR
technologies «developed»/data could be shared
OR
political pressure/Montreal Protocol/governments passing legislations βœ”
Do not accept just “collaboration”.
Do not accept any reference to 𝐢𝐹𝐢 as greenhouse gas or product of fossil fuel combustion.
Accept reference to specific measures, such as agreement on banning use/manufacture of 𝐢𝐹𝐢s.
8v. [2 marks]
𝐢𝐹𝐢s produce chlorine radicals. Write two successive propagation steps to show how chlorine
radicals catalyse the depletion of ozone.
Markscheme
𝑂3 + 𝐢𝑙 → 𝑂2 + 𝐢𝑙𝑂 βœ”
𝐢𝑙𝑂 + 𝑂 → 𝑂2 + 𝐢𝑙
OR
𝐢𝑙𝑂 + 𝑂3 → 𝐢𝑙 + 2𝑂2 βœ”
Penalize missing/incorrect radical dot (βˆ™) once only.
9a. [2 marks]
Predict the electron domain and molecular geometries around the oxygen atom of molecule A
using VSEPR
Markscheme
Electron domain geometry: tetrahedral βœ”
Molecular geometry: bent/V-shaped βœ”
9b. [1 mark]
State the type of hybridization shown by the central carbon atom in molecule B.
Markscheme
𝑠𝑝2 βœ”
9c. [1 mark]
State the number of sigma (𝜎) and pi (πœ‹) bonds around the central carbon atom in molecule B.
Markscheme
𝜎-bonds: 3
AND
πœ‹-bonds: 1 βœ”
9d. [1 mark]
The IR spectrum of one of the compounds is shown:
COBLENTZ SOCIETY. Collection © 2018 copyright by the U.S. Secretary of Commerce on behalf of
the United States of America. All rights reserved.
Deduce, giving a reason, the compound producing this spectrum.
Markscheme
B AND 𝐢 = 𝑂 absorption/1750 << π‘π‘š−1 >>
OR
B AND absence of 𝑂𝐻 /3200 − 3600 << π‘π‘š−1 π‘Žπ‘π‘ π‘œπ‘Ÿπ‘π‘‘π‘–π‘œπ‘› >> βœ”
Accept any value between 1700 − 1750 π‘π‘š−1 .
9e. [2 marks]
Compound A and B are isomers. Draw two other structural isomers with the formula 𝐢3 𝐻6 𝑂.
Markscheme
Accept any two 𝐢3 𝐻6 𝑂 isomers except for propanone and propen-2-ol:
βœ”βœ”
Penalize missing hydrogens in displayed structural formulas once only.
9f. [1 mark]
The equilibrium constant, 𝐾𝑐 , for the conversion of A to B is 1.0 × 108 in water at 298𝐾.
Deduce, giving a reason, which compound, A or B, is present in greater concentration when
equilibrium is reached.
Markscheme
𝐡 AND 𝐾𝑐 is greater than 1/large βœ”
9g. [1 mark]
Calculate the standard Gibbs free energy change, 𝐺 , in 𝐀𝐉𝐦𝐨π₯1 , for the reaction (A to B) at
298𝐾. Use sections 1 and 2 of the data booklet.
Markscheme
<< π›₯𝐺 𝛩 = −𝑅𝑇ln𝐾 = 0.00831π‘˜π½π‘šπ‘œπ‘™ −1 𝐾 −1 (298𝐾) (ln 1.0 × 108 ) =>>
−46 << π‘˜π½π‘šπ‘œπ‘™ −1 >> βœ”
9h. [3 marks]
Propanone can be synthesized in two steps from propene. Suggest the synthetic route
including all the necessary reactants and steps.
Markscheme
𝐻2 𝑂/water «and 𝐻 + » βœ”
𝐢𝐻3 𝐢𝐻(𝑂𝐻)𝐢𝐻3/propan-2-ol βœ”
𝐾2 πΆπ‘Ÿ2 𝑂7/«potassium» dichromate(VI) AND 𝐻 +
OR
𝐾𝑀𝑛𝑂4 /«acidified potassium» manganate(VII) βœ”
Accept 𝐻3 𝑂 + .
9i. [2 marks]
Propanone can be synthesized in two steps from propene.
Suggest why propanal is a minor product obtained from the synthetic route in (g)(i).
Markscheme
primary carbocation «intermediate forms»
OR
minor product «of the water addition would be» propan-1-ol
OR
anti-Markovnikov addition of water βœ”
primary alcohol/propan-1-ol oxidizes to an aldehyde/propanal βœ”
10a. [1 mark]
Outline how a catalyst increases the rate of reaction.
Markscheme
provides an alternative pathway/mechanism AND lower Ea βœ”
Accept description of how catalyst lowers Ea (e.g. “reactants adsorb on surface «of catalyst»”,
“reactant bonds weaken «when adsorbed»”).
10b. [2 marks]
Explain why an increase in temperature increases the rate of reaction.
Markscheme
more/greater proportion of molecules with E
Ea βœ”
greater frequency/probability/chance of collisions «between the molecules»
OR
more collision per unit of time/second βœ”
10c. [3 marks]
Discuss, referring to intermolecular forces present, the relative volatility of propanone and
propan-2-ol.
Markscheme
hydrogen bonding/bonds «and dipole–dipole and London/dispersion forces are present in»
propan-2-ol βœ”
dipole–dipole «and London/dispersion are present in» propanone βœ”
propan-2-ol less volatile AND hydrogen bonding/bonds stronger «than dipole–dipole »
OR
propan-2-ol less volatile AND «sum of all» intermolecular forces stronger βœ”
10d. [1 mark]
The diagram shows an unlabelled voltaic cell for the reaction
𝑃𝑏 2+ (π‘Žπ‘ž) + 𝑁𝑖(𝑠) → 𝑁𝑖 2+ (π‘Žπ‘ž) + 𝑃𝑏(𝑠)
Label the diagram with the species in the equation.
Markscheme
10e. [1 mark]
Calculate the standard cell potential, in 𝑉, for the cell at 298𝐾. Use section 24 of the data
booklet
Markscheme
<< −0.13𝑉 − (−0.26𝑉) = +>> 0.13 << 𝑉 >> βœ”
10f. [1 mark]
Calculate the standard free energy change, 𝐺 , in 𝐀𝐉, for the cell using sections 1 and 2 of the
data booklet.
Markscheme
<< π›₯𝐺 𝛩 = −𝑛𝐹𝐸 𝛩 = −2 × 96500 ×
0.13
1000
=>> −25 << π‘˜π½ >> βœ”
10g. [1 mark]
Suggest a metal that could replace nickel in a new half-cell and reverse the electron flow. Use
section 25 of the data booklet.
Markscheme
𝐡𝑖/𝐢𝑒/𝐴𝑔/𝑃𝑑/𝐻𝑔/𝑃𝑑/𝐴𝑒 βœ”
Accept 𝑆𝑏 OR 𝐴𝑠.
10h. [2 marks]
Describe the bonding in metals.
Markscheme
electrostatic attraction βœ”
between «a lattice of» metal/positive ions/cations AND «a sea of» delocalized electrons βœ”
Accept “mobile/free electrons”.
10i. [1 mark]
Nickel alloys are used in aircraft gas turbines. Suggest a physical property altered by the
addition of another metal to nickel.
Markscheme
Any of:
malleability/hardness
OR
«tensile» strength/ductility
OR
density
OR
thermal/electrical conductivity
OR
melting point
OR
thermal expansion βœ”
Do not accept corrosion/reactivity or any chemical property.
Accept other specific physical properties.
11a. [2 marks]
Consider the structures of medicinal molecules in section 37 of the data booklet.
Name two functional groups that both zanamivir and oseltamivir contain.
Markscheme
Any two:
«secondary» carboxamide/amido βœ”
ether βœ”
carbonyl βœ”
Accept amide
Accept amino/amine.
Accept alkenyl/alkene.
Do not accept formula.
11b. [2 marks]
Explain how zanamivir works as a preventative agent against flu viruses.
Markscheme
«drug» blocks/inhibits «viral» enzyme/neuraminidase/𝑁𝐴 «activity» βœ”
prevents virus from leaving/escaping host cells «thus cannot infect other cells» βœ”
Do not accept other anti-viral methods (as question is specific to Zanamivir).
11c. [1 mark]
Circle the side-chain in penicillin on the structure below.
Markscheme
βœ”
Accept a circle that does not surround the amido group.
Do not accept a circle that only surrounds the phenol group.
11d. [2 marks]
Explain, with reference to the action of penicillin, why new penicillins with different sidechains need to be produced.
Markscheme
bacterial resistance «to older penicillins/antibiotics» βœ”
prevent penicillinase/beta-lactamase/enzyme in bacterium to deactivate/open
penicillin/beta-lactam ring βœ”
Accept “antibiotic resistant bacteria” but not “antibiotic resistance” for M1.
Accept “reduce allergic reactions from from penicillin” for M2.
Award [1 max] for “increased efficiency” OR “increased stability in GIT”.
Do not accept “bacteria develop tolerance”.
11e. [2 marks]
State and explain the relative solubility of codeine in water compared to morphine and
diamorphine.
Markscheme
codeine less soluble «in water» than morphine AND more soluble than diamorphine
OR
morphine > codeine > diamorphine «in terms of solubility in water» βœ”
more/stronger/greater hydrogen/H bonding «due to more hydroxyl groups leads to greater
solubility» βœ”
11f. [1 mark]
State the natural source from which codeine, morphine and diamorphine are obtained.
Markscheme
opium poppy/plants/seeds βœ”
Accept “poppy” OR “opioid”.
12a. [2 marks]
There has been significant growth in the use of carbon nanotubes, CNT.
Explain these properties of carbon nanotubes.
Markscheme
Excellent strength: defect-free AND rigid/regular 2D/3D βœ”
Excellent conductivity: delocalized electrons βœ”
Accept “carbons/atoms are all covalently bonded to each other” for M1.
12b. [1 mark]
Alloying metals changes their properties. Suggest one property of magnesium that could be
improved by making a magnesium–CNT alloy.
Markscheme
Any of:
ductility βœ”
strength/resistance to deformation βœ”
malleability βœ”
hardness βœ”
resistance to corrosion/chemical resistance βœ”
range of working temperatures βœ”
density βœ”
Do not accept “conductivity”.
12c. [2 marks]
Pure magnesium needed for making alloys can be obtained by electrolysis of molten
magnesium chloride.
© International Baccalaureate Organization 2020.
Write the half-equations for the reactions occurring in this electrolysis.
Markscheme
Anode: 2𝐢𝑙 − → 𝐢𝑙2 (𝑔) + 2𝑒 − βœ”
Cathode: 𝑀𝑔2+ + 2𝑒 − → 𝑀𝑔(𝑙) βœ”
Accept 𝐢𝑙 − → 𝐢𝑙2 (𝑔) + 𝑒 .
Award [1 max] for correct equations at incorrect electrodes.
12d. [3 marks]
Calculate the theoretical mass of magnesium obtained if a current of 3.00𝐴 is used for 10.0
hours. Use charge (𝑄) = π‘π‘’π‘Ÿπ‘Ÿπ‘’π‘›π‘‘(𝐼) × π‘‘π‘–π‘šπ‘’(𝑑) and section 2 of the data booklet
Markscheme
<< 𝑄 = 𝐼 × π‘‘ = 3.00 × 10.0 × 3600 =>> 108000𝐢 βœ”
<<
𝑄
𝐹
108000𝐢
= 96500πΆπ‘šπ‘œπ‘™ −1 =>> 1.12 << π‘šπ‘œπ‘™ 𝑒 − >> βœ”
1.12π‘šπ‘œπ‘™
= 0.560π‘šπ‘œπ‘™π‘€π‘” >>
2
<< π‘š = 0.560π‘šπ‘œπ‘™ × 24.31π‘”π‘šπ‘œπ‘™ −1 =>> 13.6 << 𝑔 >> βœ”
<<
Award [3] for correct final answer.
12e. [1 mark]
Suggest a gas which should be continuously passed over the molten magnesium in the
electrolytic cell.
Markscheme
argon/π΄π‘Ÿ/helium/𝐻𝑒 βœ”
Accept any identified noble/inert gas.
Accept name OR formula.
Do not accept “nitrogen/𝑁2 “.
12f. [1 mark]
Zeolites can be used as catalysts in the manufacture of CNT. Explain, with reference to their
structure, the high selectivity of zeolites.
Markscheme
pores/cavities/channels/holes/cage-like structures βœ”
«only» reactants with appropriate/specific size/geometry/structure fit inside/go through/are
activated/can react βœ”
Accept “molecules/ions” for “reactants” in M2.
12g. [1 mark]
Experiments have been done to explore the nematic liquid crystal behaviour of CNT. Justify
how CNT molecules could be classified as nematic.
Markscheme
rod-shaped molecules
OR
«randomly distributed but» generally align
OR
no positional order AND have «some» directional order/pattern βœ”
Accept “linear” for “rod-shaped”.
13a. [1 mark]
Gasoline (petrol), biodiesel and ethanol are fuels.
[U.S. Department of Energy. https://afdc.energy.gov/]
Calculate the energy released, in π‘˜π½, from the complete combustion of 5.00π‘‘π‘š3 of ethanol.
Markscheme
<< 21200π‘˜π½π‘‘π‘š−3 × 5.00π‘‘π‘š3 =>> 106000/1.06 × 105 << π‘˜π½ >> βœ”
13b. [1 mark]
State a class of organic compounds found in gasoline.
Markscheme
alkane
OR
cycloalkane
OR
arene βœ”
Accept “alkene”.
Do not accept just “hydrocarbon”, since given in stem.
Do not accept “benzene/aromatic” for “arene”.
13c. [4 marks]
Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a
car. Exclude any discussion of cost.
Markscheme
Advantages: [2 max]
renewable βœ”
uses up waste «such as used cooking oil» βœ”
lower carbon footprint/carbon neutral βœ”
higher flashpoint βœ”
produces less 𝑆𝑂π‘₯ /𝑆𝑂2
OR
less polluting emissions βœ”
has lubricating properties
OR
preserves/increases lifespan of engine βœ”
increases the life of the catalytic converter βœ”
eliminates dependence on foreign suppliers βœ”
does not require pipelines/infrastructure «to produce» βœ”
relatively less destruction of habitat compared to obtaining petrochemicals βœ”
Accept “higher energy density” OR “biodegradable” for advantage.
Disadvantages: [2 max]
needs conversion/transesterification βœ”
takes time to produce/grow plants βœ”
takes up land
OR
deforestation βœ”
fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative
environmental effects βœ”
biodiversity affected
OR
loss of habitats «due to energy crop plantations» βœ”
cannot be used at low temperatures βœ”
variable quality «in production» βœ”
high viscosity/can clog/damage engines βœ”
Accept “lower specific energy” as disadvantage.
Do not accept “lower octane number” as disadvantage”.
13d. [1 mark]
A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a
mixture over the use of pure gasoline. Exclude any discussion of cost.
Markscheme
Any one:
uses up fossil fuels more slowly βœ”
lower carbon footprint/CO2 emissions βœ”
undergoes more complete combustion βœ”
produces fewer particulates βœ”
higher octane number/rating
OR
less knocking βœ”
prevents fuel injection system build up
OR
helps keep engine clean βœ”
Accept an example of a suitable advantage even if repeated from 9c.
13e. [2 marks]
Contrast the molecular structures of biodiesel and the vegetable oil from which it is formed.
Markscheme
Any two:
biodiesel has smaller molecules/single «hydrocarbon» chain AND oil has larger
molecules/multiple «hydrocarbon» chains βœ”
biodiesel is methyl/ethyl ester AND oil has «backbone of» glycerol joined to fatty acids βœ”
biodiesel contains one ester group AND oil contains three ester groups βœ”
Do not accept properties such as “less viscous” or “lower ignition point”.
13f. [1 mark]
When combusted, all three fuels can release carbon dioxide, a greenhouse gas, as well as
particulates. Contrast how carbon dioxide and particulates interact with sunlight.
Markscheme
carbon dioxide allows sunlight/short wavelength radiation to pass through AND particulates
reflect/scatter/absorb sunlight βœ”
Accept “particulates reflect/scatter/absorb sunlight AND carbon dioxide does not”.
Accept “𝐢𝑂2 absorbs 𝐼𝑅 «radiation» AND particulates reflect/scatter/absorb sunlight”.
Do not accept “traps” for “absorbs”.
13g. [2 marks]
Methane is another greenhouse gas. Contrast the reasons why methane and carbon dioxide are
considered significant greenhouse gases.
Markscheme
carbon dioxide is highly/more abundant «in the atmosphere» βœ”
methane is more effective/potent «as a greenhouse gas»
OR
methane/better/more effective at absorbing 𝐼𝑅 «radiation»
OR
methane has greater greenhouse factor
OR
methane has greater global warming potential/GWPβœ”
Accept “carbon dioxide contributes more to global warming” for M1.
13h. [1 mark]
Suggest a wavenumber absorbed by methane gas.
Markscheme
any value or range within 28503090 << π‘π‘š−1 >> βœ”
14a. [1 mark]
Calculate the energy released, in π‘˜π½, from the complete combustion of 5.00π‘‘π‘š3 of ethanol.
Markscheme
<< 21200π‘˜π½π‘‘π‘š−3 × 5.00π‘‘π‘š3 =>> 106000/1.06 × 105 << π‘˜π½ >> βœ”
14b. [1 mark]
State a class of organic compounds found in gasoline.
Markscheme
alkane
OR
cycloalkane
OR
arene βœ”
Accept “alkene”.
Do not accept just “hydrocarbon”, since given in stem.
Do not accept “benzene/aromatic” for “arene”.
14c. [4 marks]
Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a
car. Exclude any discussion of cost.
Markscheme
Advantages: [2 max]
renewable βœ”
uses up waste «such as used cooking oil» βœ”
lower carbon footprint/carbon neutral βœ”
higher flashpoint βœ”
produces less 𝑆𝑂π‘₯ /𝑆𝑂2
OR
less polluting emissions βœ”
has lubricating properties
OR
preserves/increases lifespan of engine βœ”
increases the life of the catalytic converter βœ”
eliminates dependence on foreign suppliers βœ”
does not require pipelines/infrastructure «to produce» βœ”
relatively less destruction of habitat compared to obtaining petrochemicals βœ”
Accept “higher energy density” OR “biodegradable” for advantage.
Disadvantages: [2 max]
needs conversion/transesterification βœ”
takes time to produce/grow plants βœ”
takes up land
OR
deforestation βœ”
fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative
environmental effects βœ”
biodiversity affected
OR
loss of habitats «due to energy crop plantations» βœ”
cannot be used at low temperatures βœ”
variable quality «in production» βœ”
high viscosity/can clog/damage engines βœ”
Accept “lower specific energy” as disadvantage.
Do not accept “lower octane number” as disadvantage”.
14d. [1 mark]
A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a
mixture over the use of pure gasoline. Exclude any discussion of cost.
Markscheme
Any one:
uses up fossil fuels more slowly βœ”
lower carbon footprint/CO2 emissions βœ”
undergoes more complete combustion βœ”
produces fewer particulates βœ”
higher octane number/rating
OR
less knocking βœ”
prevents fuel injection system build up
OR
helps keep engine clean βœ”
Accept an example of a suitable advantage even if repeated from 11c.
14e. [1 mark]
When combusted, all three fuels can release carbon dioxide, a greenhouse gas, as well as
particulates. Contrast how carbon dioxide and particulates interact with sunlight.
Markscheme
carbon dioxide allows sunlight/short wavelength radiation to pass through AND particulates
reflect/scatter/absorb sunlight βœ”
Accept “particulates reflect/scatter/absorb sunlight AND carbon dioxide does not”.
Accept “𝐢𝑂2 absorbs 𝐼𝑅 «radiation» AND particulates reflect/scatter/absorb sunlight”.
Do not accept “traps” for “absorbs”.
14f. [2 marks]
Methane is another greenhouse gas. Contrast the reasons why methane and carbon dioxide are
considered significant greenhouse gases.
Markscheme
carbon dioxide is highly/more abundant «in the atmosphere» βœ”
methane is more effective/potent «as a greenhouse gas»
OR
methane/better/more effective at absorbing 𝐼𝑅 «radiation»
OR
methane has greater greenhouse factor
OR
methane has greater global warming potential/GWPβœ”
Accept “carbon dioxide contributes more to global warming” for M1.
14g. [1 mark]
Suggest a wavenumber absorbed by methane gas.
Markscheme
any value or range within 28503090 << π‘π‘š−1 >> βœ”
14h. [1 mark]
Determine the relative rate of effusion of methane (π‘€π‘Ÿ = 16.05) to carbon dioxide (π‘€π‘Ÿ =
44.01), under the same conditions of temperature and pressure. Use section 1 of the data
booklet.
Markscheme
𝐢𝐻
44.01
«rate of effusion of 𝐢𝑂4 = √16.05 =>> 1.656 βœ”
2
15. [1 mark]
What is formed at the electrodes during the electrolysis of molten sodium bromide?
Markscheme
D
16. [1 mark]
Which compound is not in the same homologous series as the others?
A. C5H12
B. C6H12
C. C7H16
D. C8H18
Markscheme
B
17. [1 mark]
Where does oxidation occur in a voltaic cell?
A. positive electrode and anode
B. negative electrode and anode
C. positive electrode and cathode
D. negative electrode and cathode
Markscheme
B
18. [1 mark]
Which product will be obtained at the anode (positive electrode) when molten NaCl is
electrolysed?
A. Na (l)
B. Cl (g)
C. Cl2 (g)
D. Na (s)
Markscheme
C
19. [1 mark]
Which functional group is surrounded in the molecule?
A. hydroxyl
B. carboxyl
C. carbonyl
D. ether
Markscheme
C
20. [1 mark]
What is the IUPAC name of the following molecule?
A. 2-bromo-3-ethylbutane
B. 3-methyl-4-bromopentane
C. 2-ethyl-3-bromobutane
D. 2-bromo-3-methylpentane
Markscheme
D
21. [1 mark]
Consider the following electrochemical cell.
What happens to the ions in the salt bridge when a current flows?
A. Na+ ions flow to the zinc half-cell and SO42− ions flow to the copper half-cell.
B. Na+ ions flow to the copper half-cell and SO42− ions flow to the zinc half-cell.
C. Na+ and SO42− ions flow to the copper half-cell.
D. Na+ and SO42− ions flow to the zinc half-cell.
Markscheme
B
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© International Baccalaureate Organization 2021
International Baccalaureate® - Baccalauréat International® - Bachillerato Internacional®
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