A-Level Chemistry Practice Test 3
60 original multiple-choice questions with answers & explanations — covering the full A-Level Chemistry syllabus (AQA, Edexcel & OCR), AS & A2.
Note: These are original practice questions written in A-Level multiple-choice style — not reproduced exam questions. Use them to test your readiness for the real A-Level Chemistry exams.
📱 How to use: Try each question first, then click “Show Answer” to check. Covers the full A-Level course: atomic structure, amount of substance, bonding, energetics & thermodynamics, kinetics, equilibria, redox & electrode potentials, acids & buffers, inorganic chemistry, and organic chemistry with spectroscopy.
⚛ Atomic Structure & Periodicity
Q1An element X has two isotopes, 69X with 60.0% abundance and 71X with 40.0% abundance. What is the relative atomic mass of X?
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Correct: (B)
Ar = (0.600 × 69) + (0.400 × 71) = 41.4 + 28.4 = 69.8
Q2Which Period 3 element has the highest first ionisation energy?
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Correct: (C)
First ionisation energies increase across the period (Mg 738, Al 578, Si 787, P 1012 kJ mol^-1); P has the highest of these.
Q3What is the electronic configuration of an Fe^2+ ion?
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Correct: (A)
Fe is [Ar] 3d6 4s2; the 4s electrons are removed first when the ion forms, leaving 3d6.
Q4In a time of flight mass spectrometer, an ion of a sample with mass 64 g mol^-1 is given a kinetic energy of 8.5 × 10^-17 J. The flight tube is 1.20 m long. What is the time of flight of this ion? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct: (D)
Mass of one ion = 64 / (6.02 × 10^23) = 1.06 × 10^-25 kg. v = sqrt(2 × KE / m) = sqrt(2 × 8.5 × 10^-17 / 1.06 × 10^-25) = 4.0 × 10^4 m s^-1. t = d / v = 1.20 / (4.0 × 10^4) = 3.0 × 10^-5 s.
Q5Which Period 3 element has the highest melting point?
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Correct: (C)
Silicon has a giant covalent (macromolecular) structure with strong covalent bonds throughout, so it has a very high melting point.
⚖ Amount of Substance
Q6What is the volume occupied by 0.250 mol of a gas at 300 K and 100 kPa? (R = 8.31 J K^-1 mol^-1)
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Correct: (D)
V = nRT / p = (0.250 × 8.31 × 300) / 100000 = 6.23 × 10^-3 m^3 = 6.23 dm^3.
Q7A 25.0 cm^3 sample of 0.100 mol dm^-3 sodium hydroxide solution is exactly neutralised by 20.0 cm^3 of hydrochloric acid. What is the concentration of the acid?
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Correct: (A)
Moles of NaOH = 0.100 × 25.0 / 1000 = 2.50 × 10^-3 mol, so moles of HCl = 2.50 × 10^-3. Concentration = 2.50 × 10^-3 / (20.0 / 1000) = 0.125 mol dm^-3.
Q8In a preparation, the theoretical yield of a product is 8.00 g and the actual yield obtained is 6.40 g. What is the percentage yield?
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Correct: (B)
Percentage yield = (6.40 / 8.00) × 100 = 80%.
Q9A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. What is its empirical formula?
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Correct: (C)
Moles: C = 40.0 / 12 = 3.33; H = 6.7 / 1 = 6.7; O = 53.3 / 16 = 3.33. Ratio 1 : 2 : 1, so the empirical formula is CH2O.
Q10How many sulfate ions are present in 0.0500 mol of Al2(SO4)3?
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Correct: (A)
Each formula unit contains 3 sulfate ions, so moles of SO4^2- = 3 × 0.0500 = 0.150 mol. Number of ions = 0.150 × 6.02 × 10^23 = 9.03 × 10^22.
Q11Ethanoic acid (Mr = 60) reacts with ethanol (Mr = 46) to form ethyl ethanoate (Mr = 88) and water. What is the atom economy for the formation of the ester?
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Correct: (D)
Atom economy = 88 / (60 + 46) × 100 = 88 / 106 × 100 = 83%.
🔗 Bonding & Structure
Q12What is the shape of an SF6 molecule?
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Correct: (B)
Sulfur has 6 bonding pairs and no lone pairs in SF6, giving an octahedral shape with 90° bond angles.
Q13For sodium chloride: enthalpy of formation = -411 kJ mol^-1; enthalpy of atomisation of Na = +108 kJ mol^-1; first ionisation energy of Na = +496 kJ mol^-1; enthalpy of atomisation of chlorine (per mole of Cl atoms) = +121 kJ mol^-1; electron affinity of Cl = -349 kJ mol^-1. What is the lattice enthalpy of NaCl?
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Correct: (C)
Born-Haber cycle: -411 = 108 + 496 + 121 + (-349) + lattice enthalpy, so lattice enthalpy = -411 – 376 = -787 kJ mol^-1.
Q14Which compound has the highest boiling point?
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Correct: (A)
Methanol molecules form hydrogen bonds between molecules, which need much more energy to break than the van der Waals forces in the other compounds.
Q15Which bond is the most polar?
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Correct: (D)
Fluorine is the most electronegative element, so the H-F bond has the largest difference in electronegativity and is the most polar.
Q16Which oxide has the highest melting point?
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Correct: (B)
MgO has a giant ionic lattice with 2+ and 2- ions, giving very strong electrostatic attractions and a melting point of about 2850 °C.
Q17Which ion has the most exothermic enthalpy of hydration?
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Correct: (A)
Li^+ is the smallest ion, so it has the highest charge density, attracts water molecules most strongly and has the most exothermic enthalpy of hydration.
🔥 Energetics & Thermodynamics
Q18Burning 0.0200 mol of a fuel raises the temperature of 100 g of water by 15.0 K. The specific heat capacity of water is 4.18 J g^-1 K^-1. What is the enthalpy of combustion of the fuel?
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Correct: (C)
q = mcΔT = 100 × 4.18 × 15.0 = 6270 J. ΔH = -6270 / 0.0200 = -313500 J mol^-1 = -314 kJ mol^-1.
Q19Standard enthalpies of formation: CH4 = -75 kJ mol^-1, CO2 = -394 kJ mol^-1, H2O = -286 kJ mol^-1. What is the enthalpy of combustion of methane?
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Correct: (D)
ΔH = [(-394) + 2(-286)] – [(-75) + 0] = -966 + 75 = -891 kJ mol^-1.
Q20In which process does the entropy of the system increase?
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Correct: (B)
A gas is produced from a solid, so the number of particles and the disorder increase; the other changes all reduce disorder or reduce the number of gas molecules.
Q21A reaction has ΔH = +50.0 kJ mol^-1 and ΔS = +100 J K^-1 mol^-1. Above what temperature does the reaction become feasible?
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Correct: (A)
The reaction is feasible when ΔG = ΔH – TΔS ≤ 0, i.e. T ≥ ΔH / ΔS = 50000 / 100 = 500 K.
Q22Entropy values: N2 = 192 J K^-1 mol^-1, H2 = 131 J K^-1 mol^-1, NH3 = 193 J K^-1 mol^-1. What is ΔS for the reaction N2 + 3H2 → 2NH3?
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Correct: (C)
ΔS = 2(193) – [192 + 3(131)] = 386 – 585 = -199 J K^-1 mol^-1.
Q23Bond enthalpies: H-H = 436, Cl-Cl = 242, H-Cl = 431 kJ mol^-1. What is the enthalpy change for the reaction H2 + Cl2 → 2HCl?
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Correct: (B)
Bonds broken = 436 + 242 = 678 kJ mol^-1; bonds formed = 2 × 431 = 862 kJ mol^-1. ΔH = 678 – 862 = -184 kJ mol^-1.
⏱ Kinetics & Rate Equations
Q24In a series of experiments at constant temperature, doubling [A] doubles the rate of reaction, and doubling [B] increases the rate by a factor of 4. What is the overall order of the reaction?
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Correct: (D)
Doubling [A] doubles the rate (first order in A); doubling [B] quadruples the rate (second order in B). Overall order = 1 + 2 = 3.
Q25What are the units of the rate constant for a second-order reaction?
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Correct: (A)
Rate (mol dm^-3 s^-1) = k[A]^2, so k has units mol dm^-3 s^-1 / (mol dm^-3)^2 = mol^-1 dm^3 s^-1.
Q26A first-order reaction has a constant half-life of 20 s. The initial concentration of the reactant is 0.80 mol dm^-3. What is the concentration after 60 s?
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Correct: (C)
60 s is 3 half-lives, so the concentration halves three times: 0.80 → 0.40 → 0.20 → 0.10 mol dm^-3.
Q27A rate constant doubles when the temperature is raised from 300 K to 310 K. What is the activation energy of the reaction? (R = 8.31 J K^-1 mol^-1)
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Correct: (B)
ln(k2/k1) = -Ea/R (1/T2 – 1/T1). ln 2 = (Ea / 8.31)(1/300 – 1/310) = (Ea / 8.31)(1.075 × 10^-4). Ea = (0.693 × 8.31) / (1.075 × 10^-4) = 5.36 × 10^4 J mol^-1 = 54 kJ mol^-1.
Q28When the temperature of a gaseous reaction mixture is increased, the Maxwell-Boltzmann distribution of molecular energies changes so that
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Correct: (D)
The total area (total number of molecules) is unchanged, so the curve flattens and the peak shifts to higher energy.
⚖ Chemical Equilibria (Kc & Kp)
Q29The reaction A + B ⇌ 2C is studied in a 1.0 dm^3 flask. At equilibrium the amounts present are A = 0.60 mol, B = 0.60 mol and C = 0.80 mol. What is the value of Kc?
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Correct: (A)
Because the volume is 1.0 dm^3, the concentrations equal the mole amounts. Kc = [C]^2 / ([A][B]) = 0.80^2 / (0.60 × 0.60) = 0.64 / 0.36 = 1.78 (no units).
Q30At equilibrium in the reaction N2O4(g) ⇌ 2NO2(g), the partial pressure of N2O4 is 60 kPa and the partial pressure of NO2 is 40 kPa. What is the value of Kp?
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Correct: (C)
Kp = (pNO2)^2 / pN2O4 = 40^2 / 60 = 1600 / 60 = 26.7 kPa.
Q31For an exothermic reaction at equilibrium, what happens to the value of Kc when the temperature is increased?
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Correct: (B)
Increasing the temperature shifts the equilibrium in the endothermic (reverse) direction, so the equilibrium concentration of products falls and Kc decreases.
Q32What are the units of Kc for the equilibrium 2SO2(g) + O2(g) ⇌ 2SO3(g)?
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Correct: (D)
Kc = [SO3]^2 / ([SO2]^2 [O2]), so the units are (mol dm^-3)^2 / (mol dm^-3)^3 = mol^-1 dm^3.
Q33For the exothermic equilibrium N2(g) + 3H2(g) ⇌ 2NH3(g), which change increases the value of Kp?
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Correct: (A)
Kp depends only on temperature. Lowering the temperature shifts the equilibrium towards products in an exothermic reaction, so Kp increases. Pressure and catalysts do not change Kp.
🔋 Redox & Electrode Potentials
Q34What is the oxidation state of chromium in K2Cr2O7?
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Correct: (C)
2(+1) + 2x + 7(-2) = 0, so 2x = 12 and x = +6.
Q35E° values: Zn^2+/Zn = -0.76 V; Cu^2+/Cu = +0.34 V. What is the standard cell potential of the cell Zn | Zn^2+ || Cu^2+ | Cu?
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Correct: (B)
E°cell = E°(right) – E°(left) = 0.34 – (-0.76) = +1.10 V.
Q36Standard electrode potentials: Fe^3+/Fe^2+ = +0.77 V; I2/I^- = +0.54 V; Sn^4+/Sn^2+ = +0.15 V; Zn^2+/Zn = -0.76 V. Which species is the strongest oxidising agent?
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Correct: (D)
The strongest oxidising agent is the species in the half-equation with the most positive E° value, which is Fe^3+ (+0.77 V).
Q37E°(Fe^3+/Fe^2+) = +0.77 V and E°(I2/I^-) = +0.54 V. Which statement about the reaction of Fe^3+ ions with I^- ions is correct?
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Correct: (A)
E°cell = 0.77 – 0.54 = +0.23 V. A positive cell potential means the reaction (2Fe^3+ + 2I^- → 2Fe^2+ + I2) is feasible.
Q38A current of 2.00 A is passed for 4825 s through copper(II) sulfate solution using inert electrodes. What mass of copper is deposited at the cathode? (F = 96500 C mol^-1; Ar of Cu = 63.5)
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Correct: (C)
Q = It = 2.00 × 4825 = 9650 C = 9650 / 96500 = 0.100 mol of electrons. Cu^2+ + 2e^- → Cu, so moles of Cu = 0.0500 mol. Mass = 0.0500 × 63.5 = 3.18 g.
🧫 Acids, Bases & Buffers
Q39What is the pH of a 0.100 mol dm^-3 solution of ethanoic acid? (Ka = 1.7 × 10^-5 mol dm^-3)
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Correct: (B)
[H^+] = sqrt(Ka × c) = sqrt(1.7 × 10^-5 × 0.100) = sqrt(1.7 × 10^-6) = 1.30 × 10^-3 mol dm^-3. pH = -log(1.30 × 10^-3) = 2.88.
Q40What is the pH of a 0.0200 mol dm^-3 solution of sodium hydroxide at 298 K? (Kw = 1.0 × 10^-14 mol^2 dm^-6)
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Correct: (D)
pOH = -log(0.0200) = 1.70, so pH = 14.00 – 1.70 = 12.30.
Q41A buffer solution contains 0.200 mol of ethanoic acid and 0.100 mol of sodium ethanoate in the same volume of solution. The pKa of ethanoic acid is 4.77. What is the pH of the buffer?
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Correct: (A)
pH = pKa + log([salt] / [acid]) = 4.77 + log(0.100 / 0.200) = 4.77 – 0.30 = 4.47.
Q42A 0.100 mol dm^-3 solution of a weak acid has a pH of 3.00. What is the value of Ka for the acid?
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Correct: (C)
[H^+] = 10^-3.00 = 1.0 × 10^-3 mol dm^-3. Ka = [H^+]^2 / c = (1.0 × 10^-3)^2 / 0.100 = 1.0 × 10^-5 mol dm^-3.
Q43During the titration of a weak acid with sodium hydroxide solution, the pH at the half-neutralisation point is 4.50. What is Ka of the weak acid?
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Correct: (B)
At the half-neutralisation point [HA] = [A^-], so pH = pKa = 4.50. Ka = 10^-4.50 = 3.16 × 10^-5 mol dm^-3.
⚗ Inorganic Chemistry
Q44Which Group 2 sulfate is the least soluble in water?
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Correct: (D)
The solubility of the Group 2 sulfates decreases down the group, so BaSO4 is the least soluble (it is effectively insoluble).
Q45Which reaction occurs when the halogen is added to the halide solution?
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Correct: (A)
Chlorine is a stronger oxidising agent than bromine, so it displaces bromide ions; the halogens below in the group cannot displace those above them.
Q46What is the colour of the aqueous vanadium(IV) species VO^2+?
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Correct: (C)
The vanadium species are: +5 (VO2^+) yellow, +4 (VO^2+) blue, +3 green and +2 violet.
Q47An excess of concentrated ammonia solution is added to a pale blue solution containing [Cu(H2O)6]^2+ ions. What is observed?
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Correct: (B)
Ammonia first gives a pale blue precipitate of Cu(OH)2, which dissolves in excess ammonia to form the deep blue tetraammine complex.
Q48Sodium hydroxide solution is added to a solution containing Fe^3+ ions. What is observed?
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Correct: (D)
Fe^3+(aq) + 3OH^-(aq) → Fe(OH)3(s); iron(III) hydroxide is an orange-brown (rust-coloured) precipitate.
🛢 Organic Chemistry I
Q49What is the initiation step in the free-radical chlorination of methane?
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Correct: (A)
Ultraviolet light breaks the Cl-Cl bond homolytically to give two chlorine radicals; the other steps are propagation (B, C) and termination (D).
Q50Which halogenoalkane is hydrolysed fastest by aqueous silver nitrate solution?
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Correct: (C)
The C-I bond is the weakest carbon-halogen bond, so the iodoalkane reacts fastest (rate order: I > Br > Cl > F).
Q512-Bromopropane is heated with a concentrated solution of potassium hydroxide in ethanol. What is the main organic product?
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Correct: (B)
Ethanolic KOH at high temperature removes HBr by elimination, forming propene; aqueous KOH would give substitution to propan-2-ol instead.
Q52Hydrogen bromide is added to propene. What is the major product?
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Correct: (D)
By Markovnikov's rule, the H atom adds to the carbon already bonded to more H atoms, so the more stable secondary carbocation forms and the Br ends up on the central carbon.
Q53Propan-2-ol is heated with acidified potassium dichromate(VI) solution. What is the organic product?
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Correct: (A)
A secondary alcohol is oxidised to a ketone; propan-2-ol gives propanone, and the orange dichromate turns green.
Q54Which alcohol cannot be oxidised by acidified potassium dichromate(VI)?
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Correct: (C)
2-Methylpropan-2-ol is a tertiary alcohol; the carbon bonded to the OH group has no hydrogen atoms, so it cannot be oxidised.
🔬 Organic Chemistry II & Analysis
Q55Which compound gives a silver mirror when warmed with Tollens' reagent?
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Correct: (B)
Tollens' reagent is a mild oxidising agent that oxidises aldehydes (but not ketones), depositing silver as a mirror.
Q56Ethanoyl chloride is added to ethanol. What are the products?
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Correct: (D)
Acyl chlorides react vigorously with alcohols to form an ester and hydrogen chloride: CH3COCl + C2H5OH → CH3COOC2H5 + HCl.
Q57In the nitration of benzene using concentrated nitric acid and concentrated sulfuric acid, what is the electrophile?
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Correct: (A)
The acids react to form the nitronium ion, NO2^+, which is attacked by the delocalised pi electrons of the benzene ring.
Q58Which is the strongest base?
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Correct: (C)
The ethyl group pushes electrons towards the nitrogen, making the lone pair more available to accept a proton. In phenylamine the lone pair is delocalised into the benzene ring, making it a much weaker base.
Q59In solid glycine, which exists as a zwitterion, the groups present are
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Correct: (B)
A proton is transferred from the carboxylic acid group to the amino group within the same molecule, giving -NH3^+ and -COO^- groups.
Q60How many peaks are there in the proton NMR spectrum of ethyl ethanoate, CH3COOCH2CH3?
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Correct: (D)
There are three different proton environments: the CH3 next to the carbonyl, the CH2 next to the oxygen and the terminal CH3, so there are 3 peaks (integrals in the ratio 3 : 2 : 3).
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