Specification 9CH0. Explore a topic, practise the skill, and see where to focus next.
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Element identity is fixed by proton number. Different neutron numbers give different mass numbers without changing the element, which is the definition of isotopes.
In ClO⁻, oxygen is -2 and the ion charge is -1, so chlorine is +1. The Roman numeral names chlorine's oxidation number.
Mr 88 makes the molecular formula C4H8O2, twice the empirical formula. IR supports an ester. The 3H singlet is CH3CO-, while the 2H quartet and 3H triplet identify -OCH2CH3, giving ethyl ethanoate.
These tiles show your answers to three questions. They are a starting point, not a mastery score or grade prediction.
Correct answer: They are isotopes of the same element because they have the same proton number but different neutron numbers and masses.
Element identity is fixed by proton number. Different neutron numbers give different mass numbers without changing the element, which is the definition of isotopes.
Correct answer: ClO⁻
In ClO⁻, oxygen is -2 and the ion charge is -1, so chlorine is +1. The Roman numeral names chlorine's oxidation number.
Correct answer: Ethyl ethanoate, CH3COOCH2CH3.
Mr 88 makes the molecular formula C4H8O2, twice the empirical formula. IR supports an ester. The 3H singlet is CH3CO-, while the 2H quartet and 3H triplet identify -OCH2CH3, giving ethyl ethanoate.
For parents: look at the explanation together. A correct answer is encouraging; a missed answer gives you something specific to work on. Broader practice over time is needed to understand progress.
Across the period, added protons increase nuclear charge and electrons enter the same main shell. Similar shielding and decreasing radius strengthen nuclear attraction, so more energy is required to remove an electron.
Watch for: Do not describe Atomic Structure and the Periodic Table only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Both are non-polar molecules, so London dispersion forces dominate. The larger, more polarisable I₂ electron cloud forms stronger instantaneous and induced dipoles, requiring more energy to separate molecules.
Watch for: Do not describe Bonding only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Models can show three-dimensional arrangement but balls and sticks are not to scale; the sticks are not real bonds and apparent gaps can mislead. Models must be interpreted alongside bonding evidence.
Watch for: Do not describe Structure only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Hydrogen removes oxygen from CuO and is therefore the reducing agent; hydrogen itself is oxidised to water. Copper oxide is reduced to copper.
Watch for: Do not describe Redox I only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Additional shells increase radius and shielding. Although nuclear charge increases, the net attraction to outer electrons falls, lowering the energy required to remove both.
Watch for: Do not describe The elements of Groups 1 and 2 only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
A sound decision compares the large, evidenced microbiological benefit with chemical hazards and by-product risks, then manages those risks through controlled treatment and monitoring.
Watch for: Do not describe The elements of Group 7 (halogens) only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Silver ions reveal released halide ions by precipitation. Keeping silver nitrate conditions constant makes time-to-cloudiness comparisons attributable mainly to hydrolysis differences.
Watch for: Do not describe Analysis of inorganic compounds only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Yield measures product obtained relative to the theoretical amount, while atom economy measures the fraction of reactant atoms in the desired product. A sound choice also considers solvents, energy, toxicity, separation and actual waste.
Watch for: Do not describe Formulae, Equations and Amounts of Substance only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Members of a homologous series share a functional group. The –OH group gives alcohols their characteristic reaction pattern even though physical properties vary with chain length.
Watch for: Do not describe Introduction to organic chemistry only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Limited oxygen can produce CO and soot rather than only CO₂ and water. Carbon monoxide is colourless and toxic because it interferes with oxygen carriage.
Watch for: Do not describe Alkanes only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Feedstock recycling uses thermal or chemical processing to recover useful smaller molecules. Conditions and gas treatment matter, especially for halogenated polymers.
Watch for: Do not describe Alkenes only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Acid hydrolysis is the reverse equilibrium of esterification. Alkaline hydrolysis forms a carboxylate salt, removing the acid product and making the reaction effectively irreversible.
Watch for: Do not describe Halogenoalkanes only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Acyl chlorides undergo nucleophilic acyl substitution. Water gives an acid, alcohol gives an ester, ammonia gives a primary amide and a primary amine gives a secondary amide.
Watch for: Do not describe Alcohols only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
A proposed structure is stronger when it accounts for the molecular-ion mass and multiple plausible fragments. No single fragment necessarily identifies the whole molecule uniquely.
Watch for: Do not describe Mass spectrometry only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Positional isomers can contain the same bond types and functional groups, so their main diagnostic absorptions may be similar. Another technique or fingerprint comparison may be required.
Watch for: Do not describe Infrared (IR) spectroscopy only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Endothermic reactions absorb energy, so product enthalpy exceeds reactant enthalpy and ΔH is positive. The peak represents the transition state, not the products.
Watch for: Do not describe Energetics I only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Lower activation energy increases the fraction of collisions able to react. A catalyst participates in steps but is not consumed in the overall equation and does not change ΔH or equilibrium position.
Watch for: Do not describe Kinetics I only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Kc magnitude describes equilibrium position, not reaction rate. A large value means the concentration ratio favours products but does not prove zero reactant remains.
Watch for: Do not describe Equilibrium I only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
The reactant side has four moles of gas and the product side has two. Higher pressure favours the side with fewer gas particles, so equilibrium shifts toward ammonia; K is unchanged at constant temperature.
Watch for: Do not describe Equilibrium II only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
The approximation assumes only a small fraction dissociates. If x/[HA]initial is not small, subtracting x materially changes the denominator and a more exact treatment is needed.
Watch for: Do not describe Acid-base Equilibria only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Higher charge density strengthens electrostatic attraction between the ion and polar water molecules. This releases more energy on hydration; the same charge-and-radius factors increase lattice-enthalpy magnitude.
Watch for: Do not describe Lattice energy only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Thermodynamics indicates whether products are energetically favoured, not how quickly the pathway is crossed. A large activation barrier can leave a feasible reaction kinetically slow.
Watch for: Do not describe Entropy only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Both redox species are aqueous, so an inert conductor transfers electrons without entering the half-equation. Standard measurement uses specified concentrations.
Watch for: Do not describe Redox II only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Colour can change when ligand field and geometry change without electron transfer. Oxidation numbers and physical observations distinguish substitution from redox or precipitation.
Watch for: Do not describe Principles of transition metal chemistry only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
The record distinguishes observation from inference and uses the correct term precipitate. The ion identity can be concluded separately after applying the specified test logic.
Watch for: Do not describe Reactions of transition metal elements only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
For an elementary rate-determining step, the reacting species and powers can match the experimental rate law. Rate equations must be determined from kinetic evidence, not copied from the overall balanced equation.
Watch for: Do not describe Kinetics II only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Bifunctional monomers can react at both ends to build a chain, producing a small molecule such as water or hydrogen chloride as links form. Nylon can be made at the interface between two solutions.
Watch for: Do not describe Chirality only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Nitrous acid is generated in situ from nitrite and acid. Low temperature stabilises the diazonium ion, which then undergoes coupling with an activated aromatic ring to form the -N=N- azo link.
Watch for: Do not describe Carbonyl compounds only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
A measured equilibrium quantity can be related to the other species by mass balance and stoichiometry. Sampling must not allow the equilibrium to continue changing during analysis.
Watch for: Do not describe Carboxylic acids only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Lone-pair donation raises electron density in the aromatic system, so it attracts electrophiles more strongly. OCR requires this susceptibility explanation rather than an unsupported claim about intermediate stability.
Watch for: Do not describe Arenes — benzene only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
At high substrate concentration, enzyme–substrate complexes occupy almost all active sites. Adding more substrate cannot increase the number of available active sites, so the rate approaches a maximum set by enzyme concentration and turnover.
Watch for: Do not describe Amines, amides, amino acids and proteins only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Vacuum filtration efficiently isolates crystals. Recrystallisation uses a solvent in which product is soluble hot but sparingly soluble cold; drying is essential before a meaningful melting-point assessment.
Watch for: Do not describe Organic synthesis only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
C2H4O2 gives 2(12.0000) + 4(1.0078) + 2(15.9949) = 60.0210. C3H8O has the same nominal mass 60 but an accurate mass of 60.0573, so accurate mass distinguishes them.
Watch for: Do not describe Accurate-mass spectrometry only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Equivalent carbons share one chemical shift, so symmetry can make the number of signals smaller than the number of carbon atoms. Shift data then identifies plausible environment types.
Watch for: Do not describe Nuclear magnetic resonance (NMR) only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Two spots show the sample contains at least two soluble components. A matching Rf under the same conditions supports the presence of the reference dye, though additional evidence can strengthen identification.
Watch for: Do not describe Chromatography only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
Bromine-water decolourisation shows chemical unsaturation, while the infrared absorption supports a C=C functional group. Together they strengthen the conclusion, though neither alone fixes the complete structure.
Watch for: Do not describe Core practicals 1–8 only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
A sharp boiling result supports purity but is not conclusive, especially for close-boiling contaminants. The unexpected O-H absorption is independent evidence of water or an alcohol and warrants drying, rerunning a background and repeating analysis.
Watch for: Do not describe Core practicals 9–16 only at the observable level. Use the correct particles, bonding, energy change or quantitative relationship where the question requires it.
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Pearson Edexcel · Chemistry A-Level · A Level · Chemistry · 9CH0
Issue 3, February 2024, current August 2026
Source checked: 2026-08-30. The current official specification controls assessment requirements and option choices.
Yes. This page offers three original questions from three different skills on this exact course. Each answer has an explanation, followed by a sample heatmap showing what was correct and what to revisit. No account is needed, and taster answers are not saved.
It shows the outcome of these three answers and gives a specific skill to discuss or practise next. It is not a full assessment, a mastery score or a grade prediction. Broader practice over time is needed to understand progress.
LearningP currently maps 37 assessed areas for specification 9CH0. The visible topic map below is derived from the verified route; the current official specification remains controlling.
The verified source bank contains 426 original LearningP question records for this route. Every mapped area meets the current publication minimum and passed the latest blocker and review audit.
No. LearningP uses official specifications and assessment materials to map content and demand, while its practice questions and explanations are independently authored.
No. LearningP reports practice evidence, coverage, strengths and gaps. It does not guarantee or automatically predict examination outcomes.
Use the official Pearson Edexcel · Chemistry A-Level specification and assessment-resource pages linked on this page, together with information supplied by the learner’s school.