Chemistry Paper 3 June 2023

1. A$MnO_2 + 2C \rightarrow Mn + 2CO$
2. B$MnO_2 + C \rightarrow Mn + CO_2$
3. C$2MnO_2 + C \rightarrow 2Mn + CO_2$
4. D$MnO_2 + CO \rightarrow Mn + CO_2$

1. A−127.0 kJmol⁻¹
2. B+127.0 kJmol⁻¹
3. C+913.6 kJmol⁻¹
4. D−913.6 kJmol⁻¹

1. AGroup V
2. BGroup II
3. CGroup III
4. DGroup IV

1. Aexactly as thermodynamically stable as the manganese(IV) oxide it came from
2. Bcompletely unaffected in stability by the sign of the measured enthalpy change
3. Cless thermodynamically stable, since energy must be supplied to form it
4. Dmore thermodynamically stable than the manganese(IV) oxide it was extracted from

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1. Ano electrons remaining in its outer shell
2. Bsix electrons in its outer shell
3. Cfive electrons in its outer shell
4. Dfour electrons in its outer shell

1. A$2NaHCO_3 \rightarrow Na_2O + 2CO_2 + H_2O$
2. B$NaHCO_3 + NaCl \rightarrow Na_2CO_3 + HCl$
3. C$2NaHCO_3 \rightarrow Na_2CO_3 + CO_2 + H_2O$
4. D$NaHCO_3 \rightarrow NaOH + CO_2$

1. A0.62 g
2. B0.84 g
3. C2.16 g
4. D0.31 g

1. A0.0443 moldm⁻³
2. B0.0500 moldm⁻³
3. C0.3160 moldm⁻³
4. D0.0316 moldm⁻³

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1. Aelectrolyte, dissolved directly into the solution
2. Banode, so it dissolves into solution as Ni2+ ions
3. Csalt bridge, connecting the two half-cells
4. Dcathode, so pure nickel deposits on it directly

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1. Asodium chloride
2. Bcopper(II) sulphate
3. Cdilute sulphuric acid only
4. Dnickel(II) sulphate

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1. Astays exactly constant regardless of temperature
2. Bbecomes negative once the temperature is high enough
3. Cincreases, because the ionisation of water is endothermic
4. Ddecreases, because the ionisation of water is endothermic

1. Aa reaction that takes place without a catalyst
2. Ba reaction catalysed by the solvent used
3. Ca reaction catalysed by one of its own products
4. Da reaction that is slowed down by its own products

1. A146.4 cm³
2. B292.8 cm³
3. C366.0 cm³
4. D73.2 cm³

1. Arate = $k[A]^2[B]$
2. Brate = $k[B][C]$
3. Crate = $k[A][B]$
4. Drate = $k[A][B][C]$

1. Aprecipitation reaction
2. Bredox reaction
3. Cacid-base reaction
4. Daddition reaction

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1. Apotassium manganate(VII)
2. Bneither, since they react exactly
3. Coxalic acid
4. Dthis cannot be determined from the data given

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1. Athe pairing of two electrons in the same orbital
2. Bthe shielding of the nucleus by the inner electrons
3. Cthe inability of d electrons to take part in bonding
4. Dthe reluctance of the outer pair of s electrons to take part in bonding

1. AG is $PbCl_2$ and H is HCl
2. BG is $PbO_2$ and H is $Cl_2$
3. CG is $Pb_3O_4$ and H is $O_2$
4. DG is PbO and H is $O_2$

1. Aiodide ions are reduced to iodine by water
2. Bsodium chloride decomposes in air
3. Ciodine reacts with the water in the food
4. Diodide ions are oxidised to iodine by atmospheric oxygen

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1. Ais reversible and needs heating with a platinum catalyst
2. Bis explosive even in the dark at room temperature
3. Cdoes not occur under any conditions at all
4. Dproceeds faster than the chlorine reaction under UV light

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1. Aiodine, since it forms a more strongly coloured solution with the indicator used
2. Bboth halogens are equally strong oxidising agents in this particular comparison
3. Cneither halogen is able to oxidise Fe2+ under these particular conditions at all
4. Dbromine, since only its reaction with Fe2+ gives a positive E(cell)

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1. A$P_4O_{10}$
2. B$Al_2O_3$
3. CMgO
4. D$SiO_2$

1. A$2NH_3 + 2O_2 \rightarrow N_2O + 3H_2O$
2. B$NH_3 + 2O_2 \rightarrow HNO_3 + H_2O$
3. C$4NH_3 + 5O_2 \rightarrow 4NO + 6H_2O$
4. D$4NH_3 + 3O_2 \rightarrow 2N_2 + 6H_2O$

1. Athe sulphate is converted into a nitrate
2. Bnitrogen is lost from the soil as ammonia gas
3. Cthe soil becomes strongly acidic
4. Dthe fertiliser becomes more soluble and is washed away

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1. Athe ions formed become progressively less stable across the period
2. Bthe atoms gain extra electron shells across the period
3. Cnuclear charge increases while atomic (ionic) radius decreases
4. Dshielding by inner electrons increases sharply across the period

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1. Aoxidises haemoglobin, reducing its ability to carry oxygen
2. Bprecipitates as an insoluble salt inside the blood vessels
3. Cbinds directly and permanently to red blood cell membranes
4. Draises the blood pH to dangerously alkaline levels

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1. A66
2. B118
3. C132
4. D264

1. A$C_5H_6$
2. B$C_8H_{10}$
3. C$C_{15}H_{18}$
4. D$C_{10}H_{12}$

1. Athe purple colour is decolourised
2. Ba white precipitate is formed
3. Cthe mixture turns green and then blue
4. Dbrown fumes are evolved

1. Aelectrophilic substitution onto the carbon-carbon double bond present in the ring
2. Bhydrolysis of the hydrocarbon by the dilute aqueous acid present in the mixture
3. Coxidation (oxidative cleavage of the carbon-carbon double bond)
4. Dreduction of the hydrocarbon by the manganate(VII) ion under acidic conditions

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1. Aionic polymerisation, rather than radical addition polymerisation
2. Baddition polymerisation
3. Ccondensation polymerisation
4. Dhydrolytic polymerisation

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1. Areduced from Mn(+7) to Mn(+2), decolourising the purple solution
2. Bleft completely unchanged, acting only as a catalyst for the reaction
3. Cprecipitated directly out of solution as solid manganese dioxide
4. Doxidised from Mn(+7) to an even higher, unstable oxidation state

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1. A1
2. B2
3. C3
4. D4

1. Awarm with aqueous sodium hydroxide
2. Breduce with $LiAlH_4$ in dry ether
3. Creflux with dilute sulphuric acid
4. Dheat with $PCl_5$

1. AP > Q > R
2. BQ > R > P
3. CR > P > Q
4. DR > Q > P

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1. Athe carboxylate ion formed from R is stabilised by resonance over two oxygen atoms, more than a phenoxide ion
2. BR simply contains a benzene ring in its structure somewhere, while Q's ring is substituted differently
3. CR has a much larger relative molecular mass than Q, which alone accounts for the difference in acidity
4. DR is completely insoluble in water while Q is fully soluble in water at ordinary room temperature and pressure

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1. Athe solution turns from colourless to purple
2. Bno visible change occurs at all
3. Ceffervescence, as carbon dioxide gas is released
4. Da white precipitate forms slowly over several minutes

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1. Aan orange precipitate forms, since both aldehyde groups react
2. Ba colourless solution forms with no visible change at all, even after some time
3. Ca single deep blue precipitate forms immediately upon mixing the two solutions
4. Dvigorous effervescence is observed as a colourless gas is steadily released

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1. Aconcentrated $HNO_3$ and concentrated $H_2SO_4$ at 55 °C
2. B$NH_3$ in ethanol, heated under reflux
3. C$Br_2$ in water at room temperature
4. D$NaNO_2$ and dilute HCl at 0–5 °C

1. Awarm with aqueous sodium hydroxide
2. Breflux with methanol and concentrated sulphuric acid
3. Cheat with $PCl_5$
4. Dreflux with methanol and aqueous sodium carbonate

1. Aan $AlCl_3$ catalyst at room temperature
2. Baqueous conditions in the dark
3. Cconcentrated sulphuric acid at 55 °C
4. Dultraviolet light

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1. Astructural isomerism
2. Boptical isomerism
3. Cno isomerism, since they have different molecular formulae
4. Dgeometric (cis-trans) isomerism

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1. Aheterolytic fission of the Br-Br bond under UV light to give Br+ and Br- ions
2. Bdirect addition of Br2 across a carbon-carbon bond in the ring
3. Chomolytic fission of the Br-Br bond under UV light to give bromine radicals
4. Dprotonation of the alkane by hydrogen bromide gas under UV light conditions

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1. Athe ratio of the volumes of the two immiscible solvents used
2. Bthe ratio of the concentrations of the solute in two immiscible solvents at equilibrium
3. Cthe total mass of the solute extracted by a solvent
4. Dthe mass of the solute that dissolves in a solvent at a given temperature

1. A+2
2. B+3
3. C+4
4. D+5

1. Athe purple colour fades and a brown solution of iodine is formed
2. Ba white precipitate is formed
3. Chydrogen gas is evolved
4. Dthe purple colour remains unchanged

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1. Ahas an unusually high melting point compared with typical organic solutes
2. Bis coloured rather than colourless in both solvents used
3. Chas a very small relative molecular mass compared with the solvents
4. Dassociates or dissociates differently in the two solvents

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1. AMnO4- + 2I- + 4H+ -> Mn2+ + I2 + 2H2O
2. B2MnO4- + 5I- + 16H+ -> 2Mn2+ + 5I2 + 8H2O + O2
3. C2MnO4- + 10I- + 8H+ -> 2Mn2+ + 5I2 + 4H2O
4. D2MnO4- + 10I- + 16H+ -> 2Mn2+ + 5I2 + 8H2O

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1. Aa permanent product that remains in solution after the reaction is entirely complete
2. Ba reducing agent that is used up completely as the reaction proceeds
3. Ca spectator ion with no chemical role whatsoever in the reaction mixture
4. Dhomogeneous catalyst, being oxidised then reduced back as the reaction proceeds

1. Aallow the effluent to evaporate completely
2. Ballow solids to settle and the effluent to be treated and tested before release
3. Cincrease the volume of effluent produced
4. Ddilute the effluent with rain water

1. Aare toxic and accumulate in the bodies of living organisms
2. Braise the pH of water bodies
3. Cevaporate readily into the atmosphere
4. Dare broken down quickly by bacteria

1. Aa permanent electrical charge
2. Ba very large surface area to volume ratio and a hollow structure
3. Ca very high density
4. Da very low melting point

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1. Alowers the water's pH, killing aquatic organisms and corroding structures
2. Bhas no measurable effect at all on organisms living in the neutral water
3. Cimmediately evaporates from the river, leaving no lasting effect behind
4. Draises the water's dissolved oxygen concentration to toxic levels for fish

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1. Aboiled until all of the water evaporates, leaving the pollutants behind
2. Bmixed with an equal volume of pure water simply to dilute the pollutant concentration
3. Cpassed through a resin bed that exchanges its ions for the dissolved pollutant ions
4. Dfiltered through a bed of fine sand to physically remove all dissolved ions

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1. Acarbon nanotubes have no surface atoms available for any kind of chemical reaction whatsoever
2. Bcarbon nanotubes are naturally radioactive and bond readily to any living tissue
3. Ccarbon nanotubes dissolve completely and harmlessly in ordinary blood plasma
4. Dcarbon atoms on their surface can be chemically functionalised with target-directing groups

1. Areflect all incoming near-infrared radiation away from the tumour site entirely and completely
2. Bchemically react with tumour cells on contact to destroy them directly
3. Cphysically block blood flow to the tumour, starving it entirely of oxygen
4. Dabsorb near-infrared radiation, which penetrates tissue, and re-emit it as localised heat