A-Level Chemistry Practice Test 9
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
Q1A sample of boron contains 19.9% of the isotope ^10B and 80.1% of the isotope ^11B. What is the relative atomic mass of boron in this sample?
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Correct: (C)
(10 × 19.9 + 11 × 80.1) / 100 = (199 + 881.1) / 100 = 10.80.
Q2The first ionisation energies of magnesium and aluminium are 738 and 578 kJ mol^-1 respectively. Which statement explains why aluminium has the lower value?
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Correct: (B)
The electron removed from Al comes from the 3p sub-shell, which is at higher energy (and slightly further from the nucleus) than the 3s electron removed from Mg, so less energy is needed to remove it.
Q3How many unpaired electrons are there in an Fe^3+ ion?
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Correct: (D)
Fe is [Ar] 3d^6 4s^2. The 4s and then 3d electrons are removed to give Fe^3+ = [Ar] 3d^5, with five singly occupied d orbitals, so there are 5 unpaired electrons.
Q4Which statement about atomic radius across Period 3, from sodium to argon, is correct?
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Correct: (A)
Across the period, protons are added to the nucleus but electrons enter the same outer shell, so the effective nuclear attraction increases and the atoms get smaller.
Q5The successive ionisation energies of an element, X, show a very large increase between the third and fourth ionisation energies. In which group of the Periodic Table is X?
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Correct: (B)
The first three electrons are removed easily from the outer shell; the fourth must come from an inner shell, causing the large jump. X therefore has 3 outer-shell electrons and is in Group 13.
⚖ Amount of Substance
Q6A sample of 0.0250 mol of a gas occupies 600 cm^3 at a pressure of 100 kPa. What is the temperature of the gas? (R = 8.31 J K^-1 mol^-1)
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Correct: (B)
T = pV / nR = (1.00 × 10^5 × 6.00 × 10^-4) / (0.0250 × 8.31) = 60.0 / 0.2078 = 289 K.
Q725.0 cm^3 of 0.120 mol dm^-3 sodium hydroxide solution reacts exactly with 20.0 cm^3 of dilute sulfuric acid. What is the concentration of the acid?
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Correct: (D)
Moles of NaOH = 0.120 × 0.0250 = 3.00 × 10^-3. Since H2SO4 + 2NaOH, moles of acid = 1.50 × 10^-3. Concentration = 1.50 × 10^-3 / 0.0200 = 0.0750 mol dm^-3.
Q82.30 g of ethanol (Mr = 46.0) is dehydrated to form ethene (Mr = 28.0). The mass of ethene obtained is 1.12 g. What is the percentage yield?
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Correct: (C)
Moles of ethanol = 2.30 / 46.0 = 0.0500. Maximum mass of ethene = 0.0500 × 28.0 = 1.40 g. Percentage yield = (1.12 / 1.40) × 100 = 80.0%.
Q9Titanium is made by the reaction TiCl4 + 2Mg → Ti + 2MgCl2. What is the atom economy for the production of titanium? (Mr: TiCl4 = 189.7, Mg = 24.3, Ti = 47.9)
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Correct: (A)
Atom economy = 47.9 / (189.7 + 2 × 24.3) × 100 = 47.9 / 238.3 × 100 = 20.1%.
Q10A compound contains 40.0% carbon, 6.67% hydrogen and 53.3% oxygen by mass. What is its empirical formula?
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Correct: (A)
C: 40.0 / 12.0 = 3.33; H: 6.67 / 1.0 = 6.67; O: 53.3 / 16.0 = 3.33. The ratio is 1 : 2 : 1, so the empirical formula is CH2O.
Q11A solution of sodium sulfate is fully dissociated into ions. How many ions are present in a solution containing 0.500 mol of Na2SO4?
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Correct: (C)
Each formula unit gives 3 ions (2Na^+ + SO4^2-). Total ions = 0.500 × 3 × 6.02 × 10^23 = 9.03 × 10^23.
🔗 Bonding & Structure
Q12What are the shape and the H-N-H bond angle in an ammonia molecule?
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Correct: (D)
Nitrogen has three bonding pairs and one lone pair. The lone pair repels more strongly, compressing the bond angle to 107° and giving a trigonal pyramidal shape.
Q13Water (Mr = 18) boils at 100 °C, but hydrogen sulfide (Mr = 34) boils at -60 °C. The main reason for this difference is that
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Correct: (A)
Oxygen is small and highly electronegative, so water forms hydrogen bonds that need much extra energy to break. Sulfur is too large and not electronegative enough for hydrogen bonding in H2S.
Q14For sodium chloride, ΔHf = -411 kJ mol^-1. The enthalpy of atomisation of Na is +107 kJ mol^-1, the first ionisation energy of Na is +496 kJ mol^-1, the bond enthalpy term for 1/2 Cl2 is +121 kJ mol^-1 and the electron affinity of Cl is -349 kJ mol^-1. What is the lattice enthalpy of formation of NaCl?
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Correct: (C)
Born-Haber cycle: -411 = 107 + 496 + 121 – 349 + ΔHlatt, so ΔHlatt = -411 – 375 = -786 kJ mol^-1.
Q15Which molecule is linear?
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Correct: (B)
In CO2 the carbon has two double bonds and no lone pair, so the two electron domains repel to opposite sides, giving a linear molecule with a 180° bond angle.
Q16Which molecule has a permanent dipole?
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Correct: (D)
The C-Cl bond in CH3Cl is polar and the molecule is not symmetrical, so the bond dipoles do not cancel. In CO2, CCl4 and BF3 the dipoles cancel by symmetry.
Q17Graphite conducts electricity because
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Correct: (A)
Each carbon forms three covalent bonds; the fourth electron per atom is delocalised within the layers and can carry charge along them.
🔥 Energetics & Thermodynamics
Q1850.0 cm^3 of 1.00 mol dm^-3 hydrochloric acid is neutralised by 50.0 cm^3 of 1.00 mol dm^-3 sodium hydroxide. The temperature rises by 6.8 K. What is the enthalpy of neutralisation? (c = 4.18 J g^-1 K^-1; assume the total mass of solution is 100 g)
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Correct: (B)
q = 100 × 4.18 × 6.8 = 2842 J. Moles of water formed = 1.00 × 0.0500 = 0.0500. ΔH = -2842 / 0.0500 = -56.8 kJ mol^-1.
Q19The enthalpies of combustion are: C = -394 kJ mol^-1, H2 = -286 kJ mol^-1 and CH3OH(l) = -726 kJ mol^-1. What is the enthalpy of formation of methanol?
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Correct: (D)
ΔHf(CH3OH) = ΔHc(C) + 2ΔHc(H2) – ΔHc(CH3OH) = -394 + 2(-286) – (-726) = -966 + 726 = -240 kJ mol^-1.
Q20In which process is the entropy change of the system positive?
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Correct: (C)
A gas is produced from a solid, so the system becomes much more disordered. The other processes either form more ordered states or reduce the number of gas molecules.
Q21A reaction has ΔH = -110 kJ mol^-1 and ΔS = -140 J K^-1 mol^-1. At what temperature is ΔG = 0 for this reaction?
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Correct: (A)
At ΔG = 0, T = ΔH / ΔS = 110000 / 140 = 786 K (units must be consistent: ΔH converted to J mol^-1).
Q22Using mean bond enthalpies (C-H = 412, O=O = 498, C=O = 805, O-H = 463 kJ mol^-1), what is the enthalpy change for CH4 + 2O2 → CO2 + 2H2O?
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Correct: (B)
Bonds broken: 4(412) + 2(498) = 2644 kJ. Bonds formed: 2(805) + 4(463) = 3462 kJ. ΔH = 2644 – 3462 = -818 kJ mol^-1.
Q23For a reaction, ΔH = +50.0 kJ mol^-1 and ΔS = +200 J K^-1 mol^-1. What is the value of ΔG at 298 K?
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Correct: (D)
ΔG = ΔH – TΔS = 50.0 – 298 × 0.200 = 50.0 – 59.6 = -9.6 kJ mol^-1, so the reaction is just feasible at 298 K.
⏱ Kinetics & Rate Equations
Q24A reaction has the rate equation rate = k[A][B]^2. When [A] = 0.100 mol dm^-3 and [B] = 0.200 mol dm^-3, the rate is 4.00 × 10^-3 mol dm^-3 s^-1. What is the value and unit of k?
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Correct: (C)
k = 4.00 × 10^-3 / (0.100 × 0.200^2) = 4.00 × 10^-3 / 4.00 × 10^-3 = 1.00. The reaction is third order overall, so k has units mol^-2 dm^6 s^-1.
Q25Initial rates were measured for a reaction between X and Y: [X] = 0.10, [Y] = 0.10, rate = 2.0 × 10^-3; [X] = 0.20, [Y] = 0.10, rate = 8.0 × 10^-3; [X] = 0.10, [Y] = 0.20, rate = 2.0 × 10^-3 (concentrations in mol dm^-3, rates in mol dm^-3 s^-1). What is the rate equation?
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Correct: (A)
Doubling [X] (at constant [Y]) quadruples the rate, so the reaction is second order in X. Doubling [Y] has no effect, so it is zero order in Y.
Q26The rate of a reaction doubles when the temperature is increased from 300 K to 310 K. Estimate 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 = 53,600 J mol^-1 = 53.6 kJ mol^-1.
Q27A first-order reaction has a rate constant of 0.0693 s^-1. What is its half-life?
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Correct: (D)
t1/2 = ln 2 / k = 0.693 / 0.0693 = 10 s.
Q28The reaction NO2 + CO → NO + CO2 is proposed to occur by this mechanism: Step 1 (slow): 2NO2 → NO3 + NO; Step 2 (fast): NO3 + CO → NO2 + CO2. What is the rate equation for the reaction?
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Correct: (C)
The rate is determined by the slow (rate-determining) step, which involves two molecules of NO2, so rate = k[NO2]^2. CO appears only in the fast step, so it does not appear in the rate equation.
⚖ Chemical Equilibria (Kc & Kp)
Q29At equilibrium for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), the concentrations are [N2] = 0.100 mol dm^-3, [H2] = 0.300 mol dm^-3 and [NH3] = 0.400 mol dm^-3. What is the value of Kc?
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Correct: (B)
Kc = [NH3]^2 / ([N2][H2]^3) = 0.400^2 / (0.100 × 0.300^3) = 0.160 / 0.00270 = 59.3 mol^-2 dm^6.
Q301.00 mol of ethanoic acid and 1.00 mol of ethanol are mixed and reach equilibrium: CH3COOH + C2H5OH ⇌ CH3COOC2H5 + H2O. Kc = 4.00. How many moles of the ester are present at equilibrium?
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Correct: (A)
If x mol of ester form, Kc = x^2 / (1 – x)^2 = 4.00. Taking the square root: x / (1 – x) = 2, so x = 2 – 2x and x = 0.667 mol.
Q31For the equilibrium N2O4(g) ⇌ 2NO2(g), a sample of N2O4 is 20.0% dissociated at a total pressure of 100 kPa. What is the value of Kp?
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Correct: (C)
From 1.00 mol: 0.80 mol N2O4 and 0.40 mol NO2 remain, total 1.20 mol. p(N2O4) = (0.80/1.20) × 100 = 66.7 kPa; p(NO2) = (0.40/1.20) × 100 = 33.3 kPa. Kp = 33.3^2 / 66.7 = 16.7 kPa.
Q32For the equilibrium CaCO3(s) ⇌ CaO(s) + CO2(g), what is the correct expression for Kc?
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Correct: (A)
The concentrations of pure solids are constant and are omitted from the equilibrium expression, leaving Kc = [CO2].
Q33The forward reaction in a reversible reaction at equilibrium is exothermic. Which change occurs when the temperature is increased?
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Correct: (D)
Raising the temperature favours the endothermic (reverse) direction, so the equilibrium shifts left and Kc falls.
🔋 Redox & Electrode Potentials
Q34What is the oxidation state of sulfur in Na2S2O3?
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Correct: (B)
2(+1) + 2x + 3(-2) = 0, so 2x = +4 and x = +2 (the average oxidation state of the two sulfur atoms).
Q35The standard electrode potentials are E°(Zn^2+/Zn) = -0.76 V and E°(Cu^2+/Cu) = +0.34 V. What is the standard EMF of the cell Zn(s)|Zn^2+(aq)||Cu^2+(aq)|Cu(s)?
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Correct: (C)
E°cell = E°(right) – E°(left) = +0.34 – (-0.76) = +1.10 V.
Q36The standard electrode potentials are E°(Cl2/Cl^-) = +1.36 V, E°(Br2/Br^-) = +1.09 V, E°(Fe^3+/Fe^2+) = +0.77 V and E°(I2/I^-) = +0.54 V. Which halogen cannot oxidise Fe^2+ ions to Fe^3+ ions?
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Correct: (A)
I2/I^- has a less positive E° (+0.54 V) than Fe^3+/Fe^2+ (+0.77 V), so iodine is not a strong enough oxidising agent to oxidise Fe^2+. Chlorine, bromine and fluorine all have more positive values.
Q37Given E°(Fe^3+/Fe^2+) = +0.77 V and E°(Fe^2+/Fe) = -0.44 V, what is the value of E°(Fe^3+/Fe)?
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Correct: (D)
Weighting by the number of electrons: E° = (1 × 0.77 + 2 × (-0.44)) / 3 = (0.77 – 0.88) / 3 = -0.04 V.
Q38A current of 5.00 A is passed through aqueous copper(II) sulfate using inert electrodes. How long is needed to deposit 0.500 mol of copper? (F = 96500 C mol^-1)
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Correct: (B)
Cu^2+ + 2e^- → Cu, so charge needed = 0.500 × 2 × 96500 = 96500 C. Time = Q / I = 96500 / 5.00 = 19300 s.
🧫 Acids, Bases & Buffers
Q39Assuming both protons of sulfuric acid are fully ionised in dilute solution, what is the pH of 0.0250 mol dm^-3 H2SO4?
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Correct: (A)
[H^+] = 2 × 0.0250 = 0.0500 mol dm^-3. pH = -log(0.0500) = 1.30.
Q40The acid dissociation constant of ethanoic acid is Ka = 1.74 × 10^-5 mol dm^-3. What is the pH of a 0.100 mol dm^-3 solution of ethanoic acid?
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Correct: (D)
[H^+] = sqrt(Ka × c) = sqrt(1.74 × 10^-5 × 0.100) = 1.32 × 10^-3 mol dm^-3. pH = -log(1.32 × 10^-3) = 2.88.
Q41At 50 °C, Kw = 5.48 × 10^-14 mol^2 dm^-6. What is the pH of pure water at 50 °C?
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Correct: (B)
In pure water [H^+] = sqrt(Kw) = sqrt(5.48 × 10^-14) = 2.34 × 10^-7 mol dm^-3. pH = 6.63. The water is still neutral; Kw simply increases with temperature.
Q42A buffer solution is made by dissolving 0.200 mol of ethanoic acid and 0.300 mol of sodium ethanoate in water to give 1.00 dm^3 of solution. Ka for ethanoic acid is 1.74 × 10^-5 mol dm^-3. What is the pH of the buffer?
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Correct: (C)
[H^+] = Ka × [acid] / [salt] = 1.74 × 10^-5 × (0.200 / 0.300) = 1.16 × 10^-5 mol dm^-3. pH = 4.94.
Q4325.0 cm^3 of 0.100 mol dm^-3 ammonia solution is titrated with 0.100 mol dm^-3 hydrochloric acid. At the equivalence point the total volume is 50.0 cm^3. Kb for NH3 is 1.80 × 10^-5 mol dm^-3. What is the pH at the equivalence point?
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Correct: (A)
At equivalence the solution contains NH4^+ at 0.0500 mol dm^-3. Ka(NH4^+) = Kw / Kb = 1.00 × 10^-14 / 1.80 × 10^-5 = 5.56 × 10^-10. [H^+] = sqrt(5.56 × 10^-10 × 0.0500) = 5.27 × 10^-6, so pH = 5.28.
⚗ Inorganic Chemistry
Q44Which statement about Group 2 elements and their compounds is correct?
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Correct: (D)
Group 2 hydroxides become more soluble down the group (Mg(OH)2 is sparingly soluble, Ba(OH)2 is quite soluble). Reactivity increases, sulfate solubility decreases, and carbonate thermal stability increases down the group.
Q45Silver nitrate solution is added to separate solutions of chloride, bromide and iodide ions. Which precipitate dissolves in dilute aqueous ammonia?
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Correct: (B)
The white precipitate of AgCl dissolves in dilute ammonia. AgBr dissolves only in concentrated ammonia, and AgI is insoluble in ammonia.
Q46Which complex ion has a coordination number of 6 and a metal oxidation state of +3?
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Correct: (C)
[Fe(CN)6]^3- has six CN^- ligands (coordination number 6), and x + 6(-1) = -3 gives x = +3 for iron. The others have coordination numbers 4, 2 and 6 with oxidation states +2, +1 and +2 respectively.
Q47Excess sodium hydroxide solution is added to a solution containing Al^3+ ions. What is observed?
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Correct: (D)
Al(OH)3 is amphoteric: it first precipitates as a white solid and then dissolves in excess NaOH to form a colourless aluminate solution.
Q48Chlorine reacts with cold, dilute sodium hydroxide to form sodium chloride, sodium chlorate(I) and water. In this reaction, chlorine
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Correct: (A)
Chlorine starts at oxidation state 0 and ends at -1 in NaCl (reduced) and +1 in NaClO (oxidised). Simultaneous oxidation and reduction of the same element is disproportionation.
🛢 Organic Chemistry I
Q49Which step is a propagation step in the free-radical substitution of methane by chlorine?
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Correct: (B)
In propagation, a radical reacts with a molecule to give a product and a new radical, keeping the chain going. Option C is initiation; options A and D are termination steps.
Q50Which halogenoalkane is hydrolysed most rapidly by aqueous sodium hydroxide?
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Correct: (C)
The C-I bond is the weakest carbon-halogen bond, so iodide is the best leaving group and 1-iodobutane reacts fastest. The C-F bond is strongest, so fluorides react slowest.
Q511-bromopropane is heated with ethanolic potassium hydroxide. What is the main organic product?
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Correct: (D)
Hot ethanolic KOH acts as a base and removes HBr by elimination, forming the alkene propene. (Aqueous KOH would give substitution to propan-1-ol instead.)
Q52Propene reacts with hydrogen bromide in the absence of peroxides. What is the main product?
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Correct: (A)
Electrophilic addition follows Markovnikov's rule: the H adds to the carbon that already has more hydrogens, so Br ends up on the central carbon, giving 2-bromopropane.
Q53Propan-1-ol is oxidised with acidified potassium dichromate(VI), and the organic product is distilled off as it forms. What is the product?
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Correct: (C)
With distillation, the aldehyde (propanal) is removed before it can be oxidised further. Refluxing would give propanoic acid instead.
Q54Which alkene shows E-Z isomerism?
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Correct: (B)
In but-2-ene, each carbon of the C=C bond carries two different groups (H and CH3), so E and Z isomers exist. In the others, at least one double-bond carbon has two identical groups.
🔬 Organic Chemistry II & Analysis
Q55Which reagent can be used to distinguish between propanal and propanone because it forms a silver mirror with one of them?
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Correct: (D)
Tollens' reagent (ammoniacal silver nitrate) is reduced by aldehydes to a silver mirror. Ketones such as propanone do not react.
Q56Ethanoyl chloride reacts with ethanol. What are the products?
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Correct: (A)
Acyl chlorides react vigorously with alcohols to form esters; here CH3COCl + C2H5OH → CH3COOC2H5 + HCl.
Q57Benzene is converted into nitrobenzene using
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Correct: (C)
Nitration uses the nitronium ion, NO2^+, generated from concentrated HNO3 and concentrated H2SO4; the mixture is warmed to about 50 °C.
Q58Which of these nitrogen compounds is the strongest base?
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Correct: (B)
The ethyl group pushes electron density onto the nitrogen (+I effect), making the lone pair more available to accept a proton. In phenylamine the lone pair is delocalised into the benzene ring, so it is a much weaker base.
Q59How many signals are there in the proton NMR spectrum of propanal, CH3CH2CHO?
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Correct: (D)
Propanal has three different proton environments: the CH3 group, the CH2 group and the aldehyde CHO proton, so it gives three signals.
Q60A compound shows a very broad absorption between 2500 and 3300 cm^-1 in its infra-red spectrum. Which functional group does this indicate?
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Correct: (C)
Carboxylic acids give a characteristic very broad O-H absorption in the 2500-3300 cm^-1 region (together with a C=O peak near 1700 cm^-1).
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