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Original, AI-authored English practice with worked guidance. Selected topics only; independent teacher review is pending. This is not a complete syllabus, official past-paper collection or predicted exam score. Check your own exam-board specification: these concepts are not certified against a particular board or exam year.
76 original questions across 15 selected topic areas. No account or payment required to practise.
Cambridge International AS & A Level Chemistry (9701), examination year 2027: AI-assisted conceptual alignment to official sources, not teacher or exam-board certification. Syllabus mapping and remaining coverage.
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Original English concept practice addressing selected identified gaps. Not complete syllabus coverage or practical competence.
Question 1A supplied atmospheric mechanism has steps NO2+SO2 -> NO+SO3 and 2NO+O2 -> 2NO2. Show the net reaction after combining suitable multiples and identify the catalyst. Explain how oxidation of sulfur dioxide can contribute to acid rain. Separately write the aqueous acid-base reaction of ammonia with water.4 indicative marks
Explain using the evidence4 indicative marksNo calculator
A supplied atmospheric mechanism has steps NO2+SO2 -> NO+SO3 and 2NO+O2 -> 2NO2. Show the net reaction after combining suitable multiples and identify the catalyst. Explain how oxidation of sulfur dioxide can contribute to acid rain. Separately write the aqueous acid-base reaction of ammonia with water.
Cambridge 2027: Direct conceptual match
Original targeted concept exercise: Checked atom balance of the catalytic NO/NO2 cycle, regeneration versus intermediate definitions and ammonia proton acceptance using the specified atmospheric/acid-base content. This is conceptual placement, not completion of the entire referenced subsection.
9701: 12.1: Nitrogen chemistry and atmospheric pollutants
Doubling the first equation gives two NO2 consumed and two NO formed. The second consumes those two NO and restores two NO2, so both cancel from the overall equation.
The mechanism transfers oxygen without net consumption of NO2; it is not evidence that pollution disappears. In the separate ammonia equilibrium, charge and proton transfer balance with water as proton donor.
Self-marking points
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Twice the first step plus the second gives 2SO2+O2 -> 2SO3.
NO2 is consumed then regenerated and is a catalyst; NO is the intermediate in this chosen cycle.
Sulfur trioxide can react with water to form sulfuric acid, contributing to acidic deposition.
NH3+H2O <=> NH4+ + OH- shows ammonia accepting a proton as a weak base.
Examiner tip
These are original indicative marking points, not an official Cambridge answer key. State assumptions and connect each conclusion to the supplied evidence.
Question 2Use balanced equations to contrast the acid-base behaviour of MgO, Al2O3 and SO3. Show MgO with H+, Al2O3 with H+ and aqueous OH- forming [Al(OH)4]-, and SO3 with water. Relate the pattern to basic, amphoteric and acidic oxides. This is a paper exercise, not a laboratory procedure.4 indicative marks
Explain using the evidence4 indicative marksNo calculator
Use balanced equations to contrast the acid-base behaviour of MgO, Al2O3 and SO3. Show MgO with H+, Al2O3 with H+ and aqueous OH- forming [Al(OH)4]-, and SO3 with water. Relate the pattern to basic, amphoteric and acidic oxides. This is a paper exercise, not a laboratory procedure.
Cambridge 2027: Direct conceptual match
Original targeted concept exercise: Checked all four atom/charge balances and the specifically listed Period-3 oxides; avoids treating every oxide in the period as reacting identically with water. This is conceptual placement, not completion of the entire referenced subsection.
Balance atoms and charge independently: the aluminium/hydroxide equation has Al2, O8 and H8 on both sides and charge -2 on each.
Across Period 3 the nature of these oxides moves from predominantly basic ionic oxide through amphoteric aluminium oxide to an acidic non-metal oxide. Naming the pattern without the requested equations would not supply the evidence.
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MgO+2H+ -> Mg2+ + H2O shows a basic oxide.
Al2O3+6H+ -> 2Al3+ +3H2O shows reaction with acid.
Al2O3+2OH-+3H2O -> 2[Al(OH)4]- shows its amphoteric behaviour.
SO3+H2O -> H2SO4 illustrates an acidic oxide.
Examiner tip
These are original indicative marking points, not an official Cambridge answer key. State assumptions and connect each conclusion to the supplied evidence.
Question 3A fictional analytical report says sample X forms a white silver-halide precipitate soluble in dilute aqueous ammonia, Y forms a cream precipitate soluble only in concentrated ammonia, and Z forms a yellow precipitate insoluble in ammonia. Identify the halides and explain the trend in halogen boiling points from chlorine to iodine. Interpret the supplied observations only; do not perform tests.4 indicative marks
Explain using the evidence4 indicative marksNo calculator
A fictional analytical report says sample X forms a white silver-halide precipitate soluble in dilute aqueous ammonia, Y forms a cream precipitate soluble only in concentrated ammonia, and Z forms a yellow precipitate insoluble in ammonia. Identify the halides and explain the trend in halogen boiling points from chlorine to iodine. Interpret the supplied observations only; do not perform tests.
Cambridge 2027: Direct conceptual match
Original targeted concept exercise: Verified all three silver-halide colour/solubility pairs and inter- versus intramolecular explanation; no ammonia or silver-reagent preparation instructions. This is conceptual placement, not completion of the entire referenced subsection.
Pair each reported precipitate colour with its ammonia behaviour, rather than using one vague colour observation. The combinations distinguish the three supplied samples.
Boiling separates X2 molecules. Increasing dispersion attractions from Cl2 to I2 explains declining volatility; bond-breaking within X2 is a different process.
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X contains chloride, Y bromide and Z iodide under the stated silver-halide test interpretation.
The observations concern AgCl, AgBr and AgI respectively; colour alone should be corroborated by solubility evidence.
Larger halogen molecules down the group have more polarisable electron clouds and stronger instantaneous-dipole/induced-dipole attractions.
More energy is needed to separate molecules, so boiling points rise; this does not mean their intramolecular bonds necessarily strengthen.
Examiner tip
These are original indicative marking points, not an official Cambridge answer key. State assumptions and connect each conclusion to the supplied evidence.
Question 4A complex is [Co(NH3)4Cl2]+. Ammonia is neutral and chloride has charge -1. Determine cobalt oxidation state and coordination number, and describe the two geometrical arrangements for an octahedral complex. Explain qualitatively why changing ligands can change colour.4 indicative marks
Explain using the evidence4 indicative marksNo calculator
A complex is [Co(NH3)4Cl2]+. Ammonia is neutral and chloride has charge -1. Determine cobalt oxidation state and coordination number, and describe the two geometrical arrangements for an octahedral complex. Explain qualitatively why changing ligands can change colour.
Cambridge 2027: Direct conceptual match
Original targeted concept exercise: Checked oxidation-state/coordination distinction and octahedral cis/trans possibilities; qualitative ligand-field colour matches 28.3 without inventing a colour observation. This is conceptual placement, not completion of the entire referenced subsection.
Count attached donor atoms, not net charge, for coordination number: four ammine nitrogen donors plus two chloride donors make six.
The formula admits adjacent and opposite chloride positions. This is a structural prediction, not evidence of a measured sample colour; no numerical splitting or observed colour is supplied.
Self-marking points
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Cobalt oxidation state is +3 because x-2=+1.
Six monodentate ligands give coordination number 6 and octahedral geometry.
The two chlorides can be adjacent (cis, 90 degrees apart) or opposite (trans, 180 degrees apart).
Ligands affect d-orbital splitting; changing the energy gap changes the frequency absorbed and therefore the observed complementary colour.
Examiner tip
These are original indicative marking points, not an official Cambridge answer key. State assumptions and connect each conclusion to the supplied evidence.
