Chemistry Paper 3 November 2021

1. A$1s^2 2s^2 2p^6 3s^2 3p^4$
2. B$1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$
3. C$1s^2 2s^2 2p^6 3s^2 3p^6$
4. D$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$

1. Athe cationic charge increases
2. Bthe lattice energies become much more negative
3. Cthe hydration enthalpies become less negative while the lattice energies change little
4. Dthe sulphate ion becomes larger

1. Acarbonate ions
2. Bhalide ions
3. Csulphate ions
4. Dnitrate ions

1. AIt increases steadily down the group, as each element gains an extra occupied electron shell
2. BIt decreases steadily down the group, as the increasing nuclear charge pulls electrons in more tightly
3. CIt stays essentially constant down the group, since Group (II) atoms all have the same number of outer electrons
4. DIt increases then decreases down the group in an irregular pattern with no clear trend

1. AThe ionisation energy of every Group (II) element is identical, so ease of cation formation is unrelated to position
2. BThe nuclear charge decreases down the group, directly reducing the pull on the outer electrons
3. CIncreasing atomic radius and shielding outweigh the rise in nuclear charge, so the outer electrons are held less strongly
4. DEach atom gains extra outer electrons down the group, making them considerably easier to remove together as a pair when forming the cation

1. AThe enthalpy of solution is exactly equal to the lattice energy alone in every single case, with hydration playing no part
2. BThe enthalpy of solution is exactly equal to the hydration enthalpy alone in every single case, with the lattice energy playing no part
3. CThe enthalpy of solution equals the energy needed to break up the lattice plus the energy released on hydrating the separated ions
4. DThe enthalpy of solution cannot be calculated from lattice energy and hydration enthalpy by any Hess's law cycle

1. AIt is used to make plaster of Paris, which expands slightly and sets quickly to a hard solid for immobilising broken limbs
2. BIt is used as an antibiotic that is claimed to directly kill the bacteria responsible for a wide range of common infections
3. CIt is used as a painkiller that is absorbed rapidly through the skin to relieve muscle aches
4. DIt is used to dissolve kidney stones directly by reacting chemically with the calcium already present in the human body

1. AIt is a strong acid used to lower the pH of soils that have become too alkaline for good crop growth
2. BIt is used purely as a fertiliser that directly supplies plants with nitrogen for growth
3. CIt is used to kill weeds selectively by dissolving only their root structures on contact
4. DIt is basic and is used to neutralise soils that have become too acidic for good crop growth

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1. A100.8 g
2. B56.0 g
3. C73.0 g
4. D79.3 g

1. A40.6 %
2. B73.0 %
3. C77.6 %
4. D94.1 %

1. A$Pb_3O_4 + 6HNO_3 \rightarrow 3Pb(NO_3)_2 + 3H_2O$
2. B$Pb_3O_4 + 2HNO_3 \rightarrow Pb(NO_3)_2 + 2PbO + H_2O$
3. C$Pb_3O_4 + 8HNO_3 \rightarrow 3Pb(NO_3)_2 + 4H_2O + O_2$
4. D$Pb_3O_4 + 4HNO_3 \rightarrow 2Pb(NO_3)_2 + PbO_2 + 2H_2O$

Answer this when you sit the paper.

1. AMgO is built from doubly-charged ions with a higher charge density than the singly-charged ions in Na2O, giving stronger ionic attraction
2. BSodium has a much larger atomic radius than magnesium, which alone accounts for the difference in melting point
3. CNa2O and MgO are both said to have identical lattice types and equally high charge densities, so their melting points should in principle be the same
4. DMgO is a simple molecular solid while Na2O is a giant ionic lattice, so MgO has the much weaker forces

1. AD is ionic while E is a giant molecular structure, which is the reverse of the actual bonding in each
2. BD is said to have only weak van der Waals forces spread throughout its entire structure, while E instead has strong covalent bonds holding its whole giant structure firmly together
3. CD and E are both said to have exactly the same type of bonding throughout, so any melting point difference must be caused only by impurities
4. DD has strong covalent bonds holding its whole giant structure together, while E has only weak van der Waals forces between separate molecules

1. AThe ions in C are fixed in place in the solid lattice and can only move freely to carry charge once melted
2. BC contains no ions at all, whether solid or molten, so it is not able to conduct electricity under any conditions at all
3. CC is a metal in the solid state and loses its metallic bonding entirely as soon as it melts
4. DC conducts equally well as a solid and when molten, with no real difference between the two states

1. AIt makes all carbon compounds completely unreactive under any laboratory conditions
2. BIt is only relevant to inorganic carbon compounds such as carbonates and carbides
3. CIt is the basis for the huge variety of organic compounds and polymers that exist
4. DIt means carbon is generally unable to form compounds with any element other than hydrogen under normal conditions

1. ACarbon has an unusually large atomic radius compared with other Period 2 elements, favouring long chains
2. BCarbon's electrons are delocalised over the whole molecule, similar to how metallic bonding works
3. CCarbon atoms are thought to carry a small permanent electric charge that attracts other carbon atoms together indefinitely in a chain
4. DCarbon forms strong, stable C-C covalent bonds and can share up to four electrons, allowing extended chains and rings

1. ANeither PbO nor PbO2 reacts with the acid, so no conclusion about their relative basicity can be drawn
2. BPbO2 reacts with the acid to form a soluble salt, while PbO does not react and remains as the dark brown solid
3. CBoth PbO and PbO2 react equally well with the acid, forming two different soluble lead salts
4. DPbO reacts with the acid to form a soluble salt, while PbO2 does not react and remains as the dark brown solid

1. AIt releases carbon dioxide only, which is generally considered to have no known effect on the environment at typical atmospheric concentrations
2. BIt releases nitrogen gas, which directly poisons aquatic life in nearby rivers and lakes
3. CIt releases sulphur dioxide, which causes acid rain, damaging vegetation, corroding buildings and lowering soil pH
4. DIt releases large amounts of pure oxygen gas, which depletes the ozone layer over time

1. Athe position of equilibrium shifts so as to oppose the change
2. Bthe reaction stops until the original conditions are restored
3. Cthe value of the equilibrium constant changes to oppose the change
4. Dthe rate of the forward reaction always increases

1. A$3.86 \times 10^6$ Pa
2. B$4.22 \times 10^6$ Pa
3. C$0.36 \times 10^6$ Pa
4. D$3.41 \times 10^6$ Pa

1. A$5.0 \times 10^{-8}$ mol²dm⁻⁶
2. B$2.5 \times 10^{-7}$ mol²dm⁻⁶
3. C$5.0 \times 10^{-4}$ mol²dm⁻⁶
4. D$1.0 \times 10^{-3}$ mol²dm⁻⁶

Answer this when you sit the paper.

1. AUse a compromise temperature and pressure with an iron catalyst, and recycle unreacted gases back into the process
2. BUse the lowest possible temperature and the lowest possible pressure, since both are commonly assumed to favour maximum yield and speed together
3. CUse the highest possible temperature and pressure with no catalyst at all, to maximise the reaction rate alone
4. DDiscard all unreacted nitrogen and hydrogen after a single pass, since recycling gases is rarely considered economically worthwhile

1. ANitrates are thought to react directly with atmospheric oxygen to form explosive gases that accumulate near farmland areas
2. BNitrates evaporate directly into the atmosphere, where they destroy the ozone layer
3. CNitrates leach into water bodies, causing eutrophication that depletes oxygen and kills aquatic life
4. DNitrates make soil permanently infertile after a single application, however small

1. AThe decrease in solubility of a sparingly soluble salt when a solution already contains one of its own ions
2. BThe complete prevention of any salt from dissolving once a common solvent is added to it
3. CThe increase in solubility of a sparingly soluble salt when a solution already contains one of its own ions
4. DThe tendency of any two different salts to dissolve to exactly the same extent in the same solvent

1. ANaCl reacts chemically with sodium stearate to form an entirely new, more soluble compound
2. BNaCl lowers the temperature of the solution, which is the only way to precipitate the soap
3. CNaCl is thought to neutralise the sodium stearate solution, which some believe is otherwise too acidic to be used as soap
4. DNaCl provides a common ion (Na+), which reduces the solubility of sodium stearate and salts the soap out of solution

1. A$3Cl_2 + 6OH^- \rightarrow 5Cl^- + ClO_3^- + 3H_2O$
2. B$Cl_2 + OH^- \rightarrow HCl + ClO^-$
3. C$Cl_2 + 2OH^- \rightarrow ClO^- + ClO_3^- + H_2O$
4. D$Cl_2 + 2OH^- \rightarrow Cl^- + ClO^- + H_2O$

1. AHCl
2. BHBr
3. CHI
4. DHF

1. Ahydrogen bromide is insoluble in sulphuric acid
2. Bsodium bromide does not react with sulphuric acid
3. Chydrogen bromide decomposes at room temperature
4. Dsulphuric acid oxidises the bromide ion to bromine

1. AA reaction in which a species is reduced twice in succession by two separate reducing agents
2. BA reaction in which a species changes physical state without any change in oxidation number
3. CA reaction in which a single species is simultaneously oxidised and reduced
4. DA reaction in which two different species are each oxidised, with no reduction occurring at all

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1. AIt stays constant down the group, since all halogens have the same outer electron configuration pattern
2. BIt decreases down the group mainly because heavier halogens tend to exist as gases at room temperature under standard conditions
3. CIt increases down the group, since atomic size increases and the halogen's power to attract an electron rises
4. DIt decreases down the group, since atomic size increases and the halogen's power to attract an electron falls

1. AF-F bonds involve four shared electron pairs, while Cl-Cl bonds involve only one, making Cl-Cl inherently stronger
2. BF atoms are very small, so their non-bonding lone pairs repel each other strongly, weakening the F-F bond relative to Cl-Cl
3. CThe Cl-Cl bond is considered a double bond while the F-F bond is a single bond, which is said to account for the energy difference
4. DCl atoms are smaller than F atoms, so their lone pairs repel each other more strongly, weakening the Cl-Cl bond

1. AEach successive halogen has fewer outer electrons, reducing its ability to attract a bonding pair
2. BElectronegativity is unrelated to atomic structure and instead depends only on the halogen's colour
3. CAtomic radius increases down the group, so the nucleus attracts bonding electrons less strongly
4. DNuclear charge decreases down the group, directly weakening the pull on bonding electrons

1. Aincreases down the group because shielding increases
2. Bdecreases down the group because of the inert pair effect
3. Cincreases down the group as the atomic radius increases
4. Dis the same for all the Group (IV) elements

1. Athe $Al^{3+}$ ion has a high charge density and polarises the water molecules around it
2. Baluminium chloride is ionic while magnesium chloride is covalent
3. Caluminium chloride is insoluble in water
4. Dthe chloride ion is a stronger base in aluminium chloride

1. Aa green precipitate forms and then dissolves
2. Ba white precipitate forms and remains
3. Cthe solution remains colourless throughout
4. Da white precipitate forms and then dissolves

1. ACO2 (carbon in the +4 state) is stable, while CO (carbon in the +2 state) is less stable and a strong reducing agent
2. BCO (carbon in the +4 state) is stable, while CO2 (carbon in the +2 state) is less stable and a strong reducing agent
3. CCO2 and CO are equally stable, since both simply contain carbon bonded to oxygen atoms
4. DNeither CO2 nor CO is thermodynamically stable, and both decompose spontaneously at room temperature

Answer this when you sit the paper.

Answer this when you sit the paper.

1. AMgCl2 is ionic (Mg2+ has a low enough charge density) while AlCl3 is covalent (Al3+ has a very high charge density that polarises the chloride ion)
2. BBoth MgCl2 and AlCl3 are purely ionic, since both metals are in the same block of the Periodic Table
3. CBoth MgCl2 and AlCl3 are purely covalent, since chlorine is thought to generally form covalent bonds with most metals it reacts with
4. DCation size is thought to decrease and charge density to rise steadily down the whole group, so the carbonate ion is polarised much more strongly and decomposes at a distinctly lower temperature overall

1. AThermal stability of Group (II) carbonates is identical throughout the group and does not vary at all
2. BCation size is thought to decrease and charge density to rise down the group, so the carbonate ion is polarised more strongly and decomposes at a distinctly lower temperature
3. CThe carbonate ion itself becomes a completely different species for each successive Group (II) metal
4. DCation size increases and charge density falls down the group, so the cation polarises the carbonate ion less, requiring more heat to decompose it

1. Ais completely saturated
2. Bhas no localised carbon to carbon double bond
3. Ccannot react with electrophiles
4. Dis insoluble in water

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1. Athe carbon atoms are shielded by the hydrogen atoms
2. Bits π electrons are delocalised over the ring, giving extra stability
3. Call its carbon atoms are joined by single bonds
4. Dit has a very high boiling point

1. Aneutral
2. Bweakly acidic
3. Cstrongly acidic
4. Dstrongly basic

1. ABenzene reacts explosively with acidified KMnO4, releasing large volumes of gas
2. BBenzene does not decolourise acidified KMnO4, unlike an alkene, which would be oxidised and decolourise it
3. CBenzene is thought to rapidly decolourise acidified KMnO4 in the same way that any typical alkene compound would
4. DBenzene forms a brown precipitate with acidified KMnO4, unlike any typical alkene

Answer this when you sit the paper.

1. AIts steroid ring system is charged, so molecules attract each other by strong ionic bonds
2. BIts -OH groups form intermolecular hydrogen bonds between neighbouring estradiol molecules
3. CIt is thought to have an unusually low relative molecular mass, which is commonly assumed to raise boiling point sharply in every case
4. DIt contains no polar groups at all, so only very weak forces would be expected to hold it together

1. AA vigorous effervescence of gas is thought to be produced as the aromatic ring is completely destroyed by the bromine
2. BThe orange bromine water is decolourised as electrophilic substitution occurs on the ring, activated by the phenolic -OH group
3. CThe mixture turns from colourless to deep blue as a starch-iodine-type complex forms
4. DThe bromine water is thought to remain completely unaffected, since estradiol's aromatic ring is assumed to be deactivated by its own -OH groups

1. AIncrease the use of CFCs in refrigeration, since this is the only cost-effective cooling technology available
2. BAdd extra oxygen gas to the stratosphere, since this directly counteracts any chlorine-based ozone destruction
3. CBan or phase out CFCs, replace them with safer alternatives, and safely recover and destroy existing stocks
4. DRelease more chlorine-containing compounds into the upper atmosphere to dilute the existing concentration

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1. Aan aldehyde group and an alcohol group
2. Ba ketone group and a carboxylic acid group
3. Ca $CH_3CO-$ group and an ester group
4. Da $CH_3CH(OH)-$ group and a carboxylic acid group

1. A$CH_3CH(OH)COOH$
2. B$CH_3OCH_2COOH$
3. C$HOCH_2COOCH_3$
4. D$HOCH_2CH_2COOH$

1. Abuta-1,3-diene
2. Bbutanedioic acid
3. Cbutane-1,4-diol
4. Dbut-1-ene

1. AStructural (positional/functional-group) isomerism, since both are C8H9Cl but with the chlorine in different environments
2. BOptical isomerism, since both compounds have a chiral carbon atom bonded to four different groups
3. CGeometric (cis-trans) isomerism, since both compounds contain a restricted carbon-carbon double bond
4. DThere is thought to be no isomerism at all between A and B, since they are assumed to have completely different molecular formulae

1. AA reacts readily by nucleophilic substitution with the hydroxide ion; B is very unreactive because its own C-Cl bond is strengthened considerably by the nearby aromatic ring
2. BA is very unreactive, since the ring's delocalisation strengthens its C-Cl bond considerably; B reacts readily by nucleophilic substitution instead
3. CA and B are thought to be equally reactive towards NaOH(aq), since both are assumed to contain a single, equivalent C-Cl bond
4. DNeither A nor B reacts with NaOH(aq) under any conditions, since both are aromatic compounds

1. AOxidation, with the chlorine atoms replaced by oxygen-containing groups
2. BElectrophilic addition, with ammonia adding across a carbon-carbon double bond
3. CElimination, with hydrogen chloride removed to form a diene product
4. DNucleophilic substitution, with the chlorine atoms replaced by amine groups

1. AReact with dilute sodium hydroxide only, with no further steps needed at all
2. BReact with KCN (nucleophilic substitution to the dinitrile), then reduce with H2/Ni or LiAlH4
3. CReact directly with concentrated sulphuric acid, then cool the mixture rapidly to room temperature
4. DReact with bromine water in the dark, then heat the product strongly under reflux

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1. A$CH_3COCH_2CH_2CH_2OH$ and methanoic acid
2. B$CH_3COCH_2CH_2COOH$ and methanol
3. C$CH_3COCH_2CH_2COOH$ and methanal
4. D$CH_3CH(OH)CH_2CH_2COOCH_3$ and water

1. Aelectrophilic addition
2. Bnucleophilic addition
3. Cnucleophilic substitution
4. Dcondensation

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

1. ACN- substitutes directly for a hydrogen atom on the carbon chain next to the carbonyl group
2. BThe carbonyl carbon and CN- join by a free-radical mechanism initiated by ultraviolet light
3. CCN- attacks the electrophilic carbonyl carbon, the C=O pi bond breaks to give an alkoxide, which is then protonated
4. DH+ is thought to attack the carbonyl oxygen atom first, and CN- is then assumed to substitute directly for that oxygen atom

Answer this when you sit the paper.

1. ABasic, since it contains an amine group that can accept protons
2. BAcidic, since it contains carboxylic acid (-COOH) groups that can donate protons
3. CNeutral, since none of its functional groups can donate or accept a proton
4. DAmphoteric, since it contains equal numbers of acidic and basic functional groups

1. AAs an irritant acid it can severely irritate the eyes and mucous membranes, and cause harm at high concentrations
2. BIt is used purely as a fragrance and has no irritant properties of any kind
3. CIt is generally thought to be completely harmless to human tissue, so there would be no real safety concern with its use at all
4. DIt only affects plants and has no measurable effect on human eyes or skin whatsoever

1. A+1
2. B+2
3. C+3
4. D+6

1. A$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
2. B$Fe_2O_3 + 3H_2O \rightarrow 2Fe(OH)_3$
3. C$2Fe_2O_3 \rightarrow 4Fe + 3O_2$
4. D$Fe_2O_3 + 3CO_2 \rightarrow 2Fe + 3CO + 3O_2$

1. Athe solubility of the resin in the buffer
2. Bthe net charge on each amino acid and so how strongly it binds to the resin
3. Cthe temperature at which the column operates
4. Dthe size of the resin beads

1. ABoth Fe(OH)2 and Fe(OH)3 are equally stable in air, with neither converting into the other
2. BNeither Fe2+ nor Fe3+ forms a precipitate with sodium hydroxide solution under any conditions
3. CGreen Fe(OH)2 forms first but is readily air-oxidised to red-brown Fe(OH)3, showing the Fe3+ hydroxide is more stable
4. DRed-brown Fe(OH)3 forms first but is readily reduced back to green Fe(OH)2, showing the Fe2+ hydroxide is more stable

1. ACN- has no effect at all on the relative stability of Fe2+ and Fe3+ in aqueous solution
2. BCN- converts both Fe2+ and Fe3+ entirely into metallic iron, precipitating it from solution
3. CCN- forms strong complexes with both ions, but stabilises Fe3+ (as hexacyanoferrate(III)) relative to the aqueous ion more than Fe2+
4. DThe sample is thought to be heated slowly until only the least volatile amino acid remains behind as a solid residue at the very bottom of the column, leaving every other amino acid already eluted separately

1. AThe sample is thought to be heated slowly until only the least volatile amino acid remains behind as a solid residue at the bottom of the column, leaving the other amino acids already eluted separately beforehand
2. BThe sample passes through a column packed with a charged resin; ions exchange with the resin's counter-ions and are retained to different extents by charge and affinity, so they elute separately
3. CThe sample is frozen inside the column, and amino acids are separated purely by their different melting points
4. DThe sample passes through a column with no resin at all, and separation happens purely by gravity

1. AThey are thought to release no gases of any kind when burned, making their true environmental impact very difficult to detect directly
2. BThey are completely renewable and can be replaced as fast as they are consumed
3. CBurning them releases CO2 (a greenhouse gas) and SO2/NOx (causing acid rain), and they are non-renewable
4. DThey produce electricity less efficiently than any other known energy source, with no exceptions

Answer this when you sit the paper.

1. Athey dissolve completely in water
2. Bthey have a very large surface area to volume ratio and are easily absorbed into cells
3. Cthey have a higher density than larger particles
4. Dthey are chemically inert

1. A$OH^-$ ions
2. B$Cl^-$ ions
3. C$H^+$ ions
4. Dwater molecules

1. Aa precipitate of copper(II) chloride is formed
2. Bthe solution becomes strongly acidic
3. Ccopper(II) is reduced to copper(I)
4. Dchloride ligands replace the water ligands to form $[CuCl_4]^{2-}$

1. AA material with at least one dimension roughly in the range 1-100 millimetres
2. BAny material that is coloured black or dark grey in its natural state
3. CAny material that conducts electricity better than copper at room temperature
4. DA material with at least one dimension roughly in the range 1-100 nanometres

1. AIt permanently increases the sea's oxygen levels, which benefits marine life in every case
2. BIt poisons marine life with toxic chemicals, causes eutrophication, disrupts food chains, and can reach humans through seafood
3. CIt is generally thought to have no measurable harmful effect at all, since the sea is assumed to be large enough to dilute any waste completely
4. DIt only affects the appearance of the water, with no impact on marine organisms or ecosystems

1. ALeachate produced within the landfill can contaminate groundwater supplies
2. BLandfill sites produce no gases of any kind as the waste decomposes
3. CLandfill is the only waste disposal method that produces no unpleasant odour at all
4. DLandfill sites are sometimes claimed to increase the fertility of the surrounding soil permanently, though this is not generally true

1. ADecomposing waste produces methane, a flammable greenhouse gas
2. BLandfill sites remove unpleasant odours from the surrounding area entirely
3. CLandfill sites take up no land area at all, since waste compacts to almost nothing
4. DLandfill waste is thought to rarely attract pests or vermin under normal, well-managed circumstances

1. AIt exchanges OH- ions for harmful anions in the effluent, removing them from solution
2. BIt exchanges H+ ions for toxic metal cations in the effluent, removing them from solution
3. CIt filters out only solid particles, playing no role in removing dissolved ions
4. DIt adds extra colour to the effluent so that treatment progress can be monitored visually