Chemistry Paper 2 November 2025

1. Aliquid, since it lies between the melting plateau and the boiling plateau, where only one phase is warming up.
2. Bsolid, since region C-D comes soon after the melting plateau B-C and solids come before liquids on the graph.
3. Ca mixture of solid and liquid, since melting is still finishing off gradually through this region.
4. Dgas, since the temperature is rising and rising temperature always means the substance has become a gas.

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1. APeriod 1, since X is the very first element drawn in the wide block reading left to right.
2. Bthe transition metal (d) block, between Group II and Group III.
3. CGroup I, since X is drawn to the right of the narrow columns that represent the main groups.
4. DGroup VII, since elements drawn towards the right of a periodic table extract are always the halogens.

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1. Aneutral, because transition metals do not react with oxygen to form oxides at all.
2. Bacidic, because every element that is not in Group I or II forms an acidic oxide.
3. Camphoteric, because every transition metal oxide reacts with both acids and alkalis.
4. Dbasic, because it is an ionic metal oxide that reacts with dilute acids to form a salt and water.

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1. Aclose together but randomly arranged, free to slide past one another.
2. Bfar apart and randomly arranged, moving rapidly in every direction.
3. Cregularly arranged and widely spaced, sliding slowly past each other.
4. Dtightly packed in a regular pattern, only vibrating about fixed points.

1. Afar apart and randomly arranged, moving rapidly in every direction.
2. Bwidely spaced in a fixed regular pattern, vibrating rapidly in place.
3. Ctightly packed in a regular pattern, only vibrating about fixed points.
4. Dclose together but randomly arranged, free to slide past one another.

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1. Aan element, since it contains only one type of atom and cannot be split chemically.
2. Ban isotope, since every pure substance made of one type of atom is automatically an isotope.
3. Ca compound, since it always has a fixed chemical formula.
4. Da mixture, since it is a single pure substance with no other substances added.

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1. Aneutralisation reaction, because an acidic oxide reacts with a base to give a salt and water.
2. Boxidation reaction, because sulphur dioxide gains oxygen during the reaction.
3. Cthermal decomposition, because sodium hydroxide breaks down on heating with sulphur dioxide.
4. Ddisplacement reaction, because sodium displaces sulphur from the sulphur dioxide.

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1. Aremoves carbon dioxide from the waste gases, which is the main gas responsible for acid rain.
2. Bturns sulphur dioxide into a second harmful gas that is easier to filter out using a simple dust filter.
3. Cconverts the acidic gas into a harmless dissolved salt instead of letting it escape and dissolve in rain water.
4. Dcools waste gases down so that they can be released safely from a tall chimney without causing acid rain.

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1. Aionic, since electrons are completely transferred from one atom to the other, forming oppositely charged ions.
2. Bmetallic, since the diagram shows two atoms joined together in a lattice structure.
3. Cvan der Waals, since the ions shown are only weakly attracted to each other.
4. Dcovalent, since a full outer shell of electrons is always the result of covalent bonding.

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1. Aa solid, because covalent bonds between the ions require a huge amount of energy to break.
2. Ba gas, because ionic compounds always have very low melting and boiling points.
3. Ca liquid, because the strong forces between the ions keep them constantly sliding past one another.
4. Da solid, because a great deal of energy is needed to overcome the many strong ionic forces, giving a high melting point.

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1. Aforms a white precipitate that slowly dissolves back into solution.
2. Bis decolourised (turns from orange/brown to colourless).
3. Cturns from colourless to a deep blue colour.
4. Dbubbles vigorously and gives off a colourless gas with a pungent smell.

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1. Athe cracked gas reduces the bromine to hydrogen bromide gas, which then escapes from the solution.
2. Bthe cracked gas is an alkane, and alkanes always react rapidly with bromine water in the dark.
3. Cthe cracked gas contains a carbon to carbon double bond, which undergoes addition with the bromine.
4. Dthe cracked gas dissolves the bromine physically, without any chemical reaction taking place at all.

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1. Aan oxidation reaction, since ethene gains oxygen atoms from the steam.
2. Ba condensation reaction, since a small molecule is lost as the product forms.
3. Ca substitution reaction, since one atom in ethene is replaced by an OH group.
4. Dan addition (hydration) reaction, since water adds directly across the double bond with nothing else produced.

1. Aremoves the ethanol already present in the mealie meal before new ethanol can be fermented from it.
2. Bcools the mixture down to a temperature the yeast enzymes can survive before fermentation begins.
3. Cconverts the starch into simpler sugars that the yeast can actually ferment, and sterilises the mixture.
4. Devaporates all the water from the mealie meal so that only pure starch is left for the yeast to use.

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1. Astatic equilibrium, since nothing at all is moving or reacting once this point is reached.
2. Bcompletion, since the reaction has stopped happening in both directions.
3. Cdynamic equilibrium, since both reactions still occur but at equal, opposing rates.
4. Dsaturation, since no more product can dissolve once this point is reached.

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1. Adissolve in rain water to form acid rain, which damages lakes, forests and buildings.
2. Bsettle as a fine white dust that blocks sunlight from reaching plant leaves.
3. Ctrap heat in the atmosphere directly, causing global warming on their own.
4. Ddeplete the ozone layer, letting more ultraviolet radiation reach the ground.

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1. Aform a white precipitate with the bromine water, because C4H8 is insoluble in water.
2. Bleave the bromine water unchanged, because C4H8 is a saturated hydrocarbon with no double bond.
3. Cturn the bromine water blue-black, because C4H8 reacts with bromine the same way starch reacts with iodine.
4. Ddecolourise the bromine water, because C4H8 has a carbon to carbon double bond that adds bromine across it.

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1. Areact with the ethanol vapour, converting some of it into a more volatile compound.
2. Babsorb water vapour chemically, leaving only ethanol vapour to travel up the column.
3. Ccool the flask directly, lowering the boiling point of the ethanol so it distils over first.
4. Dprovide a large surface for repeated condensing and re-vaporising, enriching the rising vapour in ethanol.

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1. Ameasure the temperature of the vapour about to leave and be collected, confirming it is (nearly) pure ethanol.
2. Bprevent vapour from escaping up the column before it has had a chance to condense on the glass beads.
3. Cmeasure the boiling point of water, since water is the substance being collected as the distillate.
4. Dmeasure the temperature inside the flask, to know when all the liquid has finished boiling away.

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1. Acools the reacting gases, which is needed since the forward reaction is exothermic.
2. Bincreases the rate of the reverse reaction only, so more nitrogen and hydrogen are regenerated.
3. Cshifts the equilibrium towards the side with fewer gas molecules, increasing the yield of ammonia.
4. Dstops the reaction from ever reaching equilibrium, so ammonia keeps forming indefinitely.

1. Athe same yield of ammonia at equilibrium, but a much faster reaction rate than at 450 degrees C.
2. Ba higher yield of ammonia at equilibrium, but the reaction would be too slow to be worth running.
3. Ca lower yield of ammonia at equilibrium, and the reaction would also be too slow to be worth running.
4. Dthe same yield and the same rate, so temperature makes no real difference to the process at all.

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1. Acarbon dioxide and hydrogen.
2. Bnitrogen and hydrogen.
3. Cnitrogen and oxygen.
4. Doxygen and hydrogen.

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1. Anitrogen from natural gas and hydrogen from the fractional distillation of liquid air.
2. Bnitrogen from the electrolysis of brine and hydrogen from the fractional distillation of crude oil.
3. Cnitrogen from the fractional distillation of liquid air and hydrogen from natural gas reacted with steam.
4. Dnitrogen from the fractional distillation of petroleum and hydrogen from limestone heated strongly.

1. Adepletion of the ozone layer, since ammonia reacts directly with ozone high in the atmosphere.
2. Beutrophication of rivers and lakes, where excess nutrients cause algae to grow explosively, then die and decompose, using up dissolved oxygen and killing aquatic life.
3. Cglobal cooling, since burning fossil fuels for the process reflects sunlight back into space.
4. Dpermanent soil acidification, since ammonia itself is a strong acid that lowers soil pH wherever it is used.

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1. Aoxidation, then hydrolysis.
2. Bfermentation, then hydrolysis.
3. Chydrolysis, then oxidation.
4. Dhydrolysis, then reduction.

1. Areacts violently with bacteria on the skin, generating heat that both sanitizes the skin and powers an engine.
2. Bis completely unreactive, so it neither kills bacteria nor releases energy when burnt, making it safe for both uses.
3. Ckills microorganisms at a suitable concentration and evaporates quickly (suiting a sanitizer), and burns cleanly while mixing completely with petrol (suiting a fuel blend).
4. Donly dissolves in water and not in petrol, so it cannot actually be blended into petrol as a fuel at all.

1. Aheated until it vaporises and passed into a fractionating column, where each fraction condenses and is drawn off at the height matching its own boiling point range.
2. Breacted with steam, which converts the mixture directly into pure petrol and pure diesel.
3. Ccooled slowly until each hydrocarbon freezes out in turn, from the highest boiling point to the lowest.
4. Dcracked over a hot catalyst, which converts every hydrocarbon present into a single pure fraction.

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1. Aaerobic bacteria use dissolved oxygen in the sewage to burn off the organic solids completely, leaving only clean water.
2. Banaerobic bacteria digest the organic solid waste; undigested solids and dead bacteria settle as sludge, while fats and light solids float up as scum, leaving a partially clarified effluent.
3. Cthe sewage is simply filtered through a fine mesh, which physically separates scum, sludge and effluent with no bacteria involved.
4. Dultraviolet light from the inspection holes sterilises the sewage, killing the bacteria that would otherwise cause the scum and sludge to form.

1. Achemically neutralise any acids in the effluent using the alkaline rock surface before it reaches the soil.
2. Bcool the hot effluent down to the temperature of the surrounding soil before it soaks away.
3. Cevaporate the effluent completely, so that no liquid actually reaches the soil or water table at all.
4. Dlet the effluent filter slowly through the rocks and soil, where remaining solids are filtered out and soil bacteria further break down organic matter and pathogens.

1. Aallows sunlight to reach the bottom of the tank, which is needed to kill the anaerobic bacteria once digestion is complete.
2. Bgives the sewage a long enough retention time for anaerobic digestion and for solids/scum to settle and rise, before clarified effluent reaches the outlet.
3. Ckeeps the tank cool enough that anaerobic bacteria can survive, since they die at the temperatures found in a shallow tank.
4. Dreduces the total volume of sewage the tank can hold, forcing it to be emptied and cleaned out more often.

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1. Afiltration stage and the sedimentation stage.
2. Bflocculation stage and the disinfection stage.
3. Csedimentation stage and the flocculation stage.
4. Ddisinfection stage and the filtration stage.

1. Akill harmful bacteria in the water, and neutralise charges on suspended clay particles so they clump together.
2. Blower the pH of the water, and raise the pH of the water back to neutral before it is distributed.
3. Cneutralise charges on fine suspended particles so they clump into larger flocs that settle out, and kill harmful bacteria/pathogens so the water is safe to drink.
4. Dremove dissolved salts from the water, and add a pleasant taste and smell to the finished water.

1. Abecomes completely safe with no possible drawback, since chlorine cannot ever be harmful in water.
2. Bdevelops an unpleasant taste and smell, and may form harmful chlorinated by-products with organic matter.
3. Closes its disinfecting power entirely, since excess chlorine reacts with itself and cancels out.
4. Dturns cloudy and undrinkable purely from the colour of the chlorine gas itself.

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1. Aanywhere convenient, since ammonium nitrate is completely inert and cannot pose a storage danger.
2. Bin a cool, dry, well ventilated place, away from flammable materials and other reactive chemicals.
3. Cin a sealed container with a naked flame nearby, to burn off any moisture that collects on it.
4. Dpacked tightly together in the largest single mass possible, to save the most storage space.

1. Aplastics that persist for hundreds of years in landfills and oceans harm wildlife that ingest them or become entangled in them.
2. Bplastics spontaneously catch fire in landfills, which is actually a safe and controlled way to dispose of them.
3. Cplastics dissolve completely in seawater within a few weeks, releasing all their carbon at once as carbon dioxide.
4. Dplastics react with rainwater to form acid rain in the same way that sulphur dioxide does.

1. Aswitching entirely to glass and metal packaging, since these materials never require any energy at all to produce.
2. Bburning all plastic waste in the open as soon as it is collected, so that it never reaches landfills or oceans.
3. Ccollecting all plastic waste and burying it as deep as possible, with no other change to how much plastic is produced.
4. Dreducing and reusing plastic where possible, recycling what is left, and disposing of the rest in controlled landfill sites rather than open burning or dumping.

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1. Aaddition polymerisation, because the two monomers add across each other's functional groups with nothing lost.
2. Bcondensation polymerisation, because a small molecule is eliminated each time a new link forms.
3. Chydrolysis polymerisation, because water is added to break each monomer down before it joins the chain.
4. Dvulcanisation, because sulphur atoms are used to cross link A and B together.

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1. Aas an anti-corrosion coating sprayed directly onto iron and steel structures.
2. Bas a cutting tool material, since the polymer is harder than tool steel.
3. Cas an electrical conductor in household wiring.
4. Das fibres for making clothing, since the polymer is strong and resists creasing.

1. Aboth curves rise from the origin and level off at 100 cm3, with the MnO curve rising more steeply and levelling off sooner.
2. Bboth curves rise from the origin and level off at different final volumes, since MnO changes how much oxygen is produced.
3. Cthe MnO curve is a straight line through the origin that never levels off, while the other curve levels off at 100 cm3.
4. Dthe curve without MnO rises more steeply at first, since no catalyst means the reaction starts out faster.

1. Araises the temperature of the reaction mixture, giving the particles more kinetic energy.
2. Bremoves some of the hydrogen peroxide from the mixture before it has a chance to decompose.
3. Cincreases the concentration of hydrogen peroxide present at the start of the reaction.
4. Dprovides an alternative reaction pathway with a lower activation energy, so more particles react successfully on collision.

1. AMnO reacts with some of the hydrogen peroxide, using it up during decomposition.
2. Bwithout a catalyst, less hydrogen peroxide decomposes, so less oxygen gas is released.
3. Ca catalyst increases the amount of product formed without changing the reaction rate.
4. Da catalyst speeds up a reaction but does not change the amount of product it can form.

1. Astops the reaction reaching equilibrium at all, since gas reactions require a fixed pressure to proceed.
2. Bhas no effect on the position of equilibrium, since there are two gas molecules on each side of the equation.
3. Cshifts to the left, decreasing the yield of HI, since lower pressure always favours the reactants.
4. Dshifts to the right, increasing the yield of HI, since lower pressure always favours the side with more gas molecules.

1. Ahas no effect on the yield of HI, since delta H positive means temperature cannot shift the equilibrium.
2. Bshifts to the left, decreasing the yield of HI, since raising temperature always favours the reactants regardless of delta H.
3. Cshifts to the right, increasing the yield of HI, since raising temperature favours the endothermic (forward) direction.
4. Dstops the reverse reaction completely, converting all the H2 and I2 present into HI.