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 𝐶4 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, 𝐶𝐻2 = 𝐶𝐻𝐶𝐻(𝑂𝐻)𝐶𝐻3
B. butanal, 𝐶𝐻3 𝐶𝐻2 𝐶𝐻2 𝐶𝐻𝑂
C. butanone, 𝐶𝐻3 𝐶𝑂𝐶𝐻2 𝐶𝐻3
D. but-3-en-1-ol, 𝐶𝐻2 = 𝐶𝐻𝐶𝐻2 𝐶𝐻2 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 ✔
Molecular geometry: bent/V-shaped ✔
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 𝐶 = 𝑂 absorption/1750 << 𝑐𝑚−1 >>
OR
B AND absence of 𝑂𝐻 /3200 − 3600 << 𝑐𝑚−1 𝑎𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 >> ✔
Accept any value between 1700 − 1750 𝑐𝑚−1 .
6c. [2 marks]
Compound A and B are isomers. Draw two other structural isomers with the formula 𝐶3 𝐻6 𝑂.
Markscheme
Accept any two 𝐶3 𝐻6 𝑂 isomers except for propanone and propen-2-ol:
✔✔
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
𝐵 AND 𝐾𝑐 is greater than 1/large ✔
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 𝐸𝑎 ✔
Accept description of how catalyst lowers 𝐸𝑎 (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 ≥ 𝐸𝑎 ✔
greater frequency/probability/chance of collisions «between the molecules»
OR
more collision per unit of time/second ✔
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 ✔
dipole–dipole «and London/dispersion are present in» propanone ✔
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 ✔
7d. [1 mark]
The diagram shows an unlabelled voltaic cell for the reaction
𝑃𝑏 2+ (𝑎𝑞) + 𝑁𝑖(𝑠) → 𝑁𝑖 2+ (𝑎𝑞) + 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
𝐵𝑖/𝐶𝑢/𝐴𝑔/𝑃𝑑/𝐻𝑔/𝑃𝑡/𝐴𝑢 ✔
Accept 𝑆𝑏 OR 𝐴𝑠.
7f. [2 marks]
Describe the bonding in metals.
Markscheme
electrostatic attraction ✔
between «a lattice of» metal/positive ions/cations AND «a sea of» delocalized electrons ✔
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 ✔
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 ✔
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
𝐶𝑙 − AND more «electron–electron» repulsion ✔
Accept 𝐶𝑙 − AND has an extra electron.
8c. [2 marks]
Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.
Markscheme
𝐶𝑙 has a greater nuclear charge/number of protons/𝑍𝑒𝑓𝑓 «causing a stronger pull on the outer
electrons» ✔
same number of shells
OR
same «outer» energy level
OR
similar shielding ✔
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 𝑚/𝑧 = 35 and 37.
Markscheme
«two major» isotopes «of atomic mass 35 and 37» ✔
8e. [2 marks]
Explain the presence and relative abundance of the peak at 𝑚/𝑧 = 74.
Markscheme
«diatomic» molecule composed of «two» chlorine-37 atoms ✔
chlorine-37 is the least abundant «isotope»
OR
low probability of two Cl37 «isotopes» occurring in a molecule ✔
8f. [1 mark]
2.67𝑔 of manganese(IV) oxide was added to 200.0𝑐𝑚3 of 2.00𝑚𝑜𝑙𝑑𝑚−3 𝐻𝐶𝑙.
𝑀𝑛𝑂2 (𝑠) + 4𝐻𝐶𝑙(𝑎𝑞) → 𝐶𝑙2 (𝑔) + 2𝐻2 𝑂(𝑙) + 𝑀𝑛𝐶𝑙2 (𝑎𝑞)
Calculate the amount, in 𝑚𝑜𝑙, of manganese(IV) oxide added.
Markscheme
2.67𝑔
<< 86.94𝑔𝑚𝑜𝑙−1 =>> 0.0307 << 𝑚𝑜𝑙 >> ✔
8g. [2 marks]
Determine the limiting reactant, showing your calculations.
Markscheme
<< 𝑛𝐻𝐶𝑙 = 2.00𝑚𝑜𝑙𝑑𝑚−3 × 0.2000𝑑𝑚3 >>= 0.400𝑚𝑜𝑙 ✔
<<
0.400
4
=>> 0.100𝑚𝑜𝑙 AND 𝑀𝑛𝑂2 is the limiting reactant ✔
Accept other valid methods of determining the limiting reactant in M2.
8h. [1 mark]
Determine the excess amount, in 𝑚𝑜𝑙, of the other reactant.
Markscheme
<< 0.0307𝑚𝑜𝑙 × 4 = 0.123𝑚𝑜𝑙 >>
<< 0.400𝑚𝑜𝑙0.123𝑚𝑜𝑙 =>> 0.277 << 𝑚𝑜𝑙 >> ✔
8i. [1 mark]
Calculate the volume of chlorine, in 𝑑𝑚3 , produced if the reaction is conducted at standard
temperature and pressure (STP). Use section 2 of the data booklet.
Markscheme
<< 0.0307𝑚𝑜𝑙 × 22.7𝑑𝑚3 𝑚𝑜𝑙 −1 =>> 0.697 << 𝑑𝑚3 >> ✔
Accept methods employing 𝑝𝑉 = 𝑛𝑅𝑇.
8j. [2 marks]
State the oxidation state of manganese in 𝑀𝑛𝑂2 and 𝑀𝑛𝐶𝑙2 .
Markscheme
𝑀𝑛𝑂2 : +4 ✔
𝑀𝑛𝐶𝑙2 : +2 ✔
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 ✔
8l. [1 mark]
Chlorine gas reacts with water to produce hypochlorous acid and hydrochloric acid.
𝐶𝑙2 (𝑔) + 𝐻2 𝑂(𝑙) ⇌ 𝐻𝐶𝑙𝑂(𝑎𝑞) + 𝐻𝐶𝑙(𝑎𝑞)
Hypochlorous acid is considered a weak acid. Outline what is meant by the term weak acid.
Markscheme
partially dissociates/ionizes «in water» ✔
8m. [1 mark]
State the formula of the conjugate base of hypochlorous acid.
Markscheme
𝐶𝑙𝑂− ✔
8n. [1 mark]
Calculate the concentration of 𝐻 + (𝑎𝑞) in a 𝐻𝐶𝑙𝑂(𝑎𝑞) solution with a 𝑝𝐻 = 3.61.
Markscheme
<< [𝐻 + ] = 10−3.61 =>> 2.5 × 10−4 << 𝑚𝑜𝑙𝑑𝑚−3 >> ✔
8o. [1 mark]
State the type of reaction occurring when ethane reacts with chlorine to produce
chloroethane.
Markscheme
«free radical» substitution/𝑆𝑅 ✔
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/324𝑘𝐽𝑚𝑜𝑙 −1 than C–H bond/414𝑘𝐽𝑚𝑜𝑙 −1
OR
chloroethane AND contains a polar bond ✔
Accept “chloroethane AND polar”.
8q. [3 marks]
Explain the mechanism of the reaction between chloroethane and aqueous sodium hydroxide,
𝑁𝑎𝑂𝐻(𝑎𝑞), using curly arrows to represent the movement of electron pairs.
Markscheme
curly arrow going from lone pair/negative charge on 𝑂 in −OH to 𝐶 ✔
curly arrow showing 𝐶𝑙 leaving ✔
representation of transition state showing negative charge, square brackets and partial bonds
✔
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 𝐶𝑙 are not at 180°.
Do not award M3 if 𝑂𝐻 − 𝐶 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
/ 𝐶𝐻3 𝐶𝐻2 𝑂𝐶𝐻2 𝐶𝐻3 ✔
Accept (𝐶𝐻3 𝐶𝐻2 )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» ✔
0.9−1.0 AND triplet ✔
3.3−3.7 AND quartet ✔
Accept any values in the ranges.
Award [1] for two correct chemical shifts or two correct splitting patterns.
8t. [2 marks]
𝐶𝐶𝑙2 𝐹2 is a common chlorofluorocarbon, 𝐶𝐹𝐶.
Calculate the percentage by mass of chlorine in 𝐶𝐶𝑙2 𝐹2.
Markscheme
<< 𝑀(𝐶𝐶𝑙2 𝐹2 ) =>> 120.91 << 𝑔𝑚𝑜𝑙 −1 >> ✔
2×35.45𝑔𝑚𝑜𝑙−1
120.91𝑔𝑚𝑜𝑙−1
× 100% =>> 58.64 << % >> ✔
Award [2] for correct final answer.
8u. [1 mark]
Comment on how international cooperation has contributed to the lowering of 𝐶𝐹𝐶 emissions
responsible for ozone depletion.
Markscheme
Any of:
research «collaboration» for alternative technologies «to replace 𝐶𝐹𝐶s»
OR
technologies «developed»/data could be shared
OR
political pressure/Montreal Protocol/governments passing legislations ✔
Do not accept just “collaboration”.
Do not accept any reference to 𝐶𝐹𝐶 as greenhouse gas or product of fossil fuel combustion.
Accept reference to specific measures, such as agreement on banning use/manufacture of 𝐶𝐹𝐶s.
8v. [2 marks]
𝐶𝐹𝐶s produce chlorine radicals. Write two successive propagation steps to show how chlorine
radicals catalyse the depletion of ozone.
Markscheme
𝑂3 + 𝐶𝑙 → 𝑂2 + 𝐶𝑙𝑂 ✔
𝐶𝑙𝑂 + 𝑂 → 𝑂2 + 𝐶𝑙
OR
𝐶𝑙𝑂 + 𝑂3 → 𝐶𝑙 + 2𝑂2 ✔
Penalize missing/incorrect radical dot (∙) 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 ✔
Molecular geometry: bent/V-shaped ✔
9b. [1 mark]
State the type of hybridization shown by the central carbon atom in molecule B.
Markscheme
𝑠𝑝2 ✔
9c. [1 mark]
State the number of sigma (𝜎) and pi (𝜋) bonds around the central carbon atom in molecule B.
Markscheme
𝜎-bonds: 3
AND
𝜋-bonds: 1 ✔
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 𝐶 = 𝑂 absorption/1750 << 𝑐𝑚−1 >>
OR
B AND absence of 𝑂𝐻 /3200 − 3600 << 𝑐𝑚−1 𝑎𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 >> ✔
Accept any value between 1700 − 1750 𝑐𝑚−1 .
9e. [2 marks]
Compound A and B are isomers. Draw two other structural isomers with the formula 𝐶3 𝐻6 𝑂.
Markscheme
Accept any two 𝐶3 𝐻6 𝑂 isomers except for propanone and propen-2-ol:
✔✔
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
𝐵 AND 𝐾𝑐 is greater than 1/large ✔
9g. [1 mark]
Calculate the standard Gibbs free energy change, 𝐺 , in 𝐤𝐉𝐦𝐨𝐥1 , for the reaction (A to B) at
298𝐾. Use sections 1 and 2 of the data booklet.
Markscheme
<< 𝛥𝐺 𝛩 = −𝑅𝑇ln𝐾 = 0.00831𝑘𝐽𝑚𝑜𝑙 −1 𝐾 −1 (298𝐾) (ln 1.0 × 108 ) =>>
−46 << 𝑘𝐽𝑚𝑜𝑙 −1 >> ✔
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 + » ✔
𝐶𝐻3 𝐶𝐻(𝑂𝐻)𝐶𝐻3/propan-2-ol ✔
𝐾2 𝐶𝑟2 𝑂7/«potassium» dichromate(VI) AND 𝐻 +
OR
𝐾𝑀𝑛𝑂4 /«acidified potassium» manganate(VII) ✔
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 ✔
primary alcohol/propan-1-ol oxidizes to an aldehyde/propanal ✔
10a. [1 mark]
Outline how a catalyst increases the rate of reaction.
Markscheme
provides an alternative pathway/mechanism AND lower Ea ✔
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 ✔
greater frequency/probability/chance of collisions «between the molecules»
OR
more collision per unit of time/second ✔
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 ✔
dipole–dipole «and London/dispersion are present in» propanone ✔
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 ✔
10d. [1 mark]
The diagram shows an unlabelled voltaic cell for the reaction
𝑃𝑏 2+ (𝑎𝑞) + 𝑁𝑖(𝑠) → 𝑁𝑖 2+ (𝑎𝑞) + 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 >> ✔
10f. [1 mark]
Calculate the standard free energy change, 𝐺 , in 𝐤𝐉, for the cell using sections 1 and 2 of the
data booklet.
Markscheme
<< 𝛥𝐺 𝛩 = −𝑛𝐹𝐸 𝛩 = −2 × 96500 ×
0.13
1000
=>> −25 << 𝑘𝐽 >> ✔
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
𝐵𝑖/𝐶𝑢/𝐴𝑔/𝑃𝑑/𝐻𝑔/𝑃𝑡/𝐴𝑢 ✔
Accept 𝑆𝑏 OR 𝐴𝑠.
10h. [2 marks]
Describe the bonding in metals.
Markscheme
electrostatic attraction ✔
between «a lattice of» metal/positive ions/cations AND «a sea of» delocalized electrons ✔
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 ✔
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 ✔
ether ✔
carbonyl ✔
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» ✔
prevents virus from leaving/escaping host cells «thus cannot infect other cells» ✔
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
✔
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» ✔
prevent penicillinase/beta-lactamase/enzyme in bacterium to deactivate/open
penicillin/beta-lactam ring ✔
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» ✔
more/stronger/greater hydrogen/H bonding «due to more hydroxyl groups leads to greater
solubility» ✔
11f. [1 mark]
State the natural source from which codeine, morphine and diamorphine are obtained.
Markscheme
opium poppy/plants/seeds ✔
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 ✔
Excellent conductivity: delocalized electrons ✔
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 ✔
strength/resistance to deformation ✔
malleability ✔
hardness ✔
resistance to corrosion/chemical resistance ✔
range of working temperatures ✔
density ✔
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: 2𝐶𝑙 − → 𝐶𝑙2 (𝑔) + 2𝑒 − ✔
Cathode: 𝑀𝑔2+ + 2𝑒 − → 𝑀𝑔(𝑙) ✔
Accept 𝐶𝑙 − → 𝐶𝑙2 (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) = 𝑐𝑢𝑟𝑟𝑒𝑛𝑡(𝐼) × 𝑡𝑖𝑚𝑒(𝑡) and section 2 of the data booklet
Markscheme
<< 𝑄 = 𝐼 × 𝑡 = 3.00 × 10.0 × 3600 =>> 108000𝐶 ✔
<<
𝑄
𝐹
108000𝐶
= 96500𝐶𝑚𝑜𝑙 −1 =>> 1.12 << 𝑚𝑜𝑙 𝑒 − >> ✔
1.12𝑚𝑜𝑙
= 0.560𝑚𝑜𝑙𝑀𝑔 >>
2
<< 𝑚 = 0.560𝑚𝑜𝑙 × 24.31𝑔𝑚𝑜𝑙 −1 =>> 13.6 << 𝑔 >> ✔
<<
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/𝐴𝑟/helium/𝐻𝑒 ✔
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 ✔
«only» reactants with appropriate/specific size/geometry/structure fit inside/go through/are
activated/can react ✔
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 ✔
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 𝑘𝐽, from the complete combustion of 5.00𝑑𝑚3 of ethanol.
Markscheme
<< 21200𝑘𝐽𝑑𝑚−3 × 5.00𝑑𝑚3 =>> 106000/1.06 × 105 << 𝑘𝐽 >> ✔
13b. [1 mark]
State a class of organic compounds found in gasoline.
Markscheme
alkane
OR
cycloalkane
OR
arene ✔
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 ✔
uses up waste «such as used cooking oil» ✔
lower carbon footprint/carbon neutral ✔
higher flashpoint ✔
produces less 𝑆𝑂𝑥 /𝑆𝑂2
OR
less polluting emissions ✔
has lubricating properties
OR
preserves/increases lifespan of engine ✔
increases the life of the catalytic converter ✔
eliminates dependence on foreign suppliers ✔
does not require pipelines/infrastructure «to produce» ✔
relatively less destruction of habitat compared to obtaining petrochemicals ✔
Accept “higher energy density” OR “biodegradable” for advantage.
Disadvantages: [2 max]
needs conversion/transesterification ✔
takes time to produce/grow plants ✔
takes up land
OR
deforestation ✔
fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative
environmental effects ✔
biodiversity affected
OR
loss of habitats «due to energy crop plantations» ✔
cannot be used at low temperatures ✔
variable quality «in production» ✔
high viscosity/can clog/damage engines ✔
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 ✔
lower carbon footprint/CO2 emissions ✔
undergoes more complete combustion ✔
produces fewer particulates ✔
higher octane number/rating
OR
less knocking ✔
prevents fuel injection system build up
OR
helps keep engine clean ✔
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 ✔
biodiesel is methyl/ethyl ester AND oil has «backbone of» glycerol joined to fatty acids ✔
biodiesel contains one ester group AND oil contains three ester groups ✔
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 ✔
Accept “particulates reflect/scatter/absorb sunlight AND carbon dioxide does not”.
Accept “𝐶𝑂2 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» ✔
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/GWP✔
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 << 𝑐𝑚−1 >> ✔
14a. [1 mark]
Calculate the energy released, in 𝑘𝐽, from the complete combustion of 5.00𝑑𝑚3 of ethanol.
Markscheme
<< 21200𝑘𝐽𝑑𝑚−3 × 5.00𝑑𝑚3 =>> 106000/1.06 × 105 << 𝑘𝐽 >> ✔
14b. [1 mark]
State a class of organic compounds found in gasoline.
Markscheme
alkane
OR
cycloalkane
OR
arene ✔
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 ✔
uses up waste «such as used cooking oil» ✔
lower carbon footprint/carbon neutral ✔
higher flashpoint ✔
produces less 𝑆𝑂𝑥 /𝑆𝑂2
OR
less polluting emissions ✔
has lubricating properties
OR
preserves/increases lifespan of engine ✔
increases the life of the catalytic converter ✔
eliminates dependence on foreign suppliers ✔
does not require pipelines/infrastructure «to produce» ✔
relatively less destruction of habitat compared to obtaining petrochemicals ✔
Accept “higher energy density” OR “biodegradable” for advantage.
Disadvantages: [2 max]
needs conversion/transesterification ✔
takes time to produce/grow plants ✔
takes up land
OR
deforestation ✔
fertilizers/pesticides/phosphates/nitrates «used in production of crops» have negative
environmental effects ✔
biodiversity affected
OR
loss of habitats «due to energy crop plantations» ✔
cannot be used at low temperatures ✔
variable quality «in production» ✔
high viscosity/can clog/damage engines ✔
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 ✔
lower carbon footprint/CO2 emissions ✔
undergoes more complete combustion ✔
produces fewer particulates ✔
higher octane number/rating
OR
less knocking ✔
prevents fuel injection system build up
OR
helps keep engine clean ✔
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 ✔
Accept “particulates reflect/scatter/absorb sunlight AND carbon dioxide does not”.
Accept “𝐶𝑂2 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» ✔
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/GWP✔
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 << 𝑐𝑚−1 >> ✔
14h. [1 mark]
Determine the relative rate of effusion of methane (𝑀𝑟 = 16.05) to carbon dioxide (𝑀𝑟 =
44.01), under the same conditions of temperature and pressure. Use section 1 of the data
booklet.
Markscheme
𝐶𝐻
44.01
«rate of effusion of 𝐶𝑂4 = √16.05 =>> 1.656 ✔
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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