Free A-Level Chemistry Practice Exam (PDF)

This free A-Level Chemistry practice exam covers the content shared by AQA, OCR and Edexcel: mass spectrometry, molecular shapes, bond enthalpies and Born–Haber cycles, rate equations and the Arrhenius plot, Le Chatelier's principle, pH, electrode potentials and periodic trends in the multiple choice, then three structured questions — a titration with an ideal-gas and atom-economy calculation, an esterification equilibrium leading into weak-acid pH and a buffer, and organic mechanisms with isomerism and spectroscopy. Each solution is written as a mark scheme, showing the mole ratios, units and precise mechanism language that separate full marks from partial credit. View it online or download the print-ready PDF; no account needed.

1. Question 11 mark · Atomic structure & periodicity
   The mass spectrum of a sample of gallium shows two peaks, at $m/z = 69$ and $m/z = 71$, with relative abundances in the ratio 3 : 2. The relative atomic mass of this sample of gallium is
   • A.
     69.4
   • B.
     69.8
   • C.
     70.0
   • D.
     70.2
2. Question 21 mark · Bonding & shapes
   Xenon has eight electrons in its outer shell. What are the shape of the $\mathrm{XeF_4}$ molecule and the F–Xe–F bond angle?
   • A.
     Tetrahedral, $109.5^\circ$
   • B.
     Square planar, $90^\circ$
   • C.
     Octahedral, $90^\circ$
   • D.
     See-saw (distorted tetrahedral), $90^\circ$ and $120^\circ$
3. Question 31 mark · Energetics
   Mean bond enthalpies: $\mathrm{N \equiv N}$ 945 kJ mol$^{-1}$, $\mathrm{H{-}H}$ 436 kJ mol$^{-1}$, $\mathrm{N{-}H}$ 391 kJ mol$^{-1}$. The enthalpy change for the reaction $\mathrm{N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)}$ is
   • A.
     -93$ kJ mol$^{-1}

     LaTeX syntax issue: KaTeX parse error: Can't use function '$' in math mode at position 4: -93$̲ kJ mol$^{-1}
   • B.
     +93$ kJ mol$^{-1}

     LaTeX syntax issue: KaTeX parse error: Can't use function '$' in math mode at position 4: +93$̲ kJ mol$^{-1}
   • C.
     -965$ kJ mol$^{-1}

     LaTeX syntax issue: KaTeX parse error: Can't use function '$' in math mode at position 5: -965$̲ kJ mol$^{-1}
   • D.
     +1080$ kJ mol$^{-1}

     LaTeX syntax issue: KaTeX parse error: Can't use function '$' in math mode at position 6: +1080$̲ kJ mol$^{-1}
4. Question 41 mark · Energetics
   In the Born–Haber cycle for magnesium oxide, which of the following enthalpy changes is exothermic?
   • A.
     The second ionisation energy of magnesium
   • B.
     The second electron affinity of oxygen
   • C.
     The first electron affinity of oxygen
   • D.
     The enthalpy of atomisation of magnesium
5. Question 51 mark · Kinetics
   In a series of experiments, doubling the concentration of reactant A (with B unchanged) doubles the initial rate, and doubling the concentration of B (with A unchanged) quadruples the initial rate. With concentrations in mol dm$^{-3}$ and time in seconds, the units of the rate constant $k$ are
   • A.
     mol$^{-2}$ dm$^{6}$ s$^{-1}$
   • B.
     mol$^{-1}$ dm$^{3}$ s$^{-1}$
   • C.
     s$^{-1}$
   • D.
     mol$^{2}$ dm$^{-6}$ s$^{-1}$
6. Question 61 mark · Kinetics
   The Arrhenius equation is $k = A e^{-E_a / RT}$. A student plots $\ln k$ on the vertical axis against $\frac{1}{T}$ on the horizontal axis. The gradient of the straight line obtained is
   • A.
     $-E_a$
   • B.
     $-\frac{E_a}{R}$
   • C.
     $\frac{E_a}{R}$
   • D.
     $\ln A$
7. Question 71 mark · Equilibria
   Dinitrogen tetroxide dissociates in a closed container: $\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$, $\Delta H = +57$ kJ mol$^{-1}$. Which change increases both the equilibrium yield of $\mathrm{NO_2}$ and the value of $K_p$?
   • A.
     Increasing the temperature at constant pressure
   • B.
     Increasing the pressure at constant temperature
   • C.
     Decreasing the temperature at constant pressure
   • D.
     Adding a catalyst
8. Question 81 mark · Acids & bases
   Barium hydroxide, $\mathrm{Ba(OH)_2}$, is a strong base. The pH of a $0.050$ mol dm$^{-3}$ solution of barium hydroxide at 298 K ($K_w = 1.0 \times 10^{-14}$ mol$^2$ dm$^{-6}$) is
   • A.
     1.0
   • B.
     12.7
   • C.
     13.0
   • D.
     13.3
9. Question 91 mark · Electrode potentials & redox
   Standard electrode potentials: $\mathrm{Zn^{2+}/Zn}$ $-0.76$ V; $\mathrm{Fe^{2+}/Fe}$ $-0.44$ V; $\mathrm{Cu^{2+}/Cu}$ $+0.34$ V; $\mathrm{Ag^{+}/Ag}$ $+0.80$ V. Which statement is correct?
   • A.
     Copper metal can reduce silver ions to silver
   • B.
     $\mathrm{Fe^{2+}}$ ions are a stronger oxidising agent than $\mathrm{Cu^{2+}}$ ions
   • C.
     A cell made from the $\mathrm{Zn^{2+}/Zn}$ and $\mathrm{Cu^{2+}/Cu}$ half-cells has an EMF of 0.42 V
   • D.
     Silver is the strongest reducing agent of the four metals
10. Question 101 mark · Atomic structure & periodicity
    Which statement about trends in group 2 or group 7 is correct?
    • A.
      The solubility of the group 2 sulfates increases down the group
    • B.
      Bromine displaces iodine from aqueous potassium iodide
    • C.
      The reducing power of the halide ions decreases from fluoride to iodide
    • D.
      Magnesium reacts vigorously with cold water
11. Question 1110 marks · Amount of substance
    A student standardises a solution of hydrochloric acid using anhydrous sodium carbonate. She dissolves 2.65 g of $\mathrm{Na_2CO_3}$ ($M_r = 106.0$) in water and makes the solution up to 250 cm$^3$ in a volumetric flask. She titrates 25.0 cm$^3$ portions of this solution with the hydrochloric acid using methyl orange indicator; the mean titre is 23.50 cm$^3$. Equation: $\mathrm{Na_2CO_3 + 2HCl \rightarrow 2NaCl + H_2O + CO_2}$.
    (a)

    Calculate the concentration, in mol dm$^{-3}$, of the sodium carbonate solution.

    [2]
    (b)

    Calculate the concentration, in mol dm$^{-3}$, of the hydrochloric acid.

    [3]
    (c)

    Calculate the volume of carbon dioxide, in cm$^3$, produced during one titration at 298 K and 100 kPa. ($R = 8.31$ J K$^{-1}$ mol$^{-1}$.)

    [2]
    (d)

    Each burette reading has an uncertainty of $\pm 0.05$ cm$^3$. Calculate the percentage uncertainty in the mean titre.

    [1]
    (e)

    Sodium carbonate is manufactured by a process whose overall equation is $\mathrm{CaCO_3 + 2NaCl \rightarrow Na_2CO_3 + CaCl_2}$. Calculate the percentage atom economy for the production of sodium carbonate. ($A_r$: Na 23.0, Cl 35.5, Ca 40.1, C 12.0, O 16.0.)

    [2]
12. Question 1210 marks · Acids & bases
    Ethanoic acid is a weak acid with $K_a = 1.74 \times 10^{-5}$ mol dm$^{-3}$ at 298 K. In the presence of an acid catalyst it reacts reversibly with ethanol to form ethyl ethanoate: $\mathrm{CH_3COOH + C_2H_5OH \rightleftharpoons CH_3COOC_2H_5 + H_2O}$.
    (a)

    1.00 mol of ethanoic acid and 1.00 mol of ethanol are mixed with a trace of acid catalyst and left to reach equilibrium at 298 K. At equilibrium 0.333 mol of ethanoic acid remains. Write the expression for $K_c$ and calculate its value.

    [3]
    (b)

    More ethanol is added to the equilibrium mixture at the same temperature. State and explain the effect on the amount of ester at equilibrium and on the value of $K_c$.

    [2]
    (c)

    Calculate the pH of a $0.100$ mol dm$^{-3}$ solution of ethanoic acid at 298 K.

    [3]
    (d)

    A buffer solution is made by mixing 500 cm$^3$ of $0.100$ mol dm$^{-3}$ ethanoic acid with 500 cm$^3$ of $0.200$ mol dm$^{-3}$ sodium ethanoate. Calculate the pH of the buffer.

    [2]
13. Question 1310 marks · Organic chemistry
    2-Bromobutane, $\mathrm{CH_3CHBrCH_2CH_3}$, can be made by reacting hydrogen bromide with but-2-ene. 2-Bromobutane reacts with warm aqueous sodium hydroxide to form compound K, and with hot ethanolic potassium hydroxide to form a mixture of two alkenes.
    (a)

    Name the mechanism of the reaction between hydrogen bromide and but-2-ene, and describe in words how the mechanism proceeds.

    [3]
    (b)

    Name the mechanism of the reaction between 2-bromobutane and warm aqueous sodium hydroxide, and describe in words how the mechanism proceeds.

    [3]
    (c)

    Name compound K and the two alkenes formed with ethanolic potassium hydroxide. State which of the two alkenes shows E/Z isomerism and explain why the other does not.

    [2]
    (d)

    The infrared spectrum of K shows a broad absorption at about 3300 cm$^{-1}$ that is absent from the spectrum of 2-bromobutane. Identify the bond responsible, and state the number of peaks in the carbon-13 NMR spectrum of K.

    [2]

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