Chemistry questions and solutions

Browse original practice and official past-paper questions. Each question has its own link, with its source and worked solution.

364 questions · Page 10 of 16

1. Q8 · Original practice · 1 mark
   A monoprotic acid has $pK_a=4.20$. At pH 5.20, the ratio of conjugate base to undissociated acid is
   Acids, bases and titration
2. Q9 · Original practice · 1 mark
   A weak monoprotic acid is titrated with sodium hydroxide at $25^\circ\mathrm C$. Which statement about the equivalence point is correct?
   Acids, bases and titration
3. Q10 · Original practice · 1 mark
   An indicator has $K_a=1.0\times10^{-8}$. Its approximate colour-change range is
   Acids, bases and titration
4. Q11 · Original practice · 1 mark
   What is the oxidation state of sulfur in $\mathrm{S_2O_3^{2-}}$, averaged over the two sulfur atoms?
   Redox and electrochemistry
5. Q12 · Original practice · 1 mark
   A galvanic cell uses zinc and copper half-cells. Which statement is correct?
   Redox and electrochemistry
6. Q13 · Original practice · 1 mark
   The standard reduction potentials of $\mathrm{Ag^+/Ag}$ and $\mathrm{Cu^{2+}/Cu}$ are +0.80 V and +0.34 V. The standard cell potential of their spontaneous galvanic cell is
   Redox and electrochemistry
7. Q14 · Original practice · 1 mark
   A molten mixture containing only sodium chloride is electrolysed using inert electrodes. The products are
   Redox and electrochemistry
8. Q15 · Original practice · 1 mark
   When a spoon is electroplated with silver, the spoon should be connected to the
   Redox and electrochemistry
9. Q16 · Original practice · 1 mark
   The same charge is passed through separate $\mathrm{AgNO_3}$ and $\mathrm{CuSO_4}$ solutions. Assume 100% current efficiency. The mole ratio of deposited silver to deposited copper is
   Redox and electrochemistry
10. Q17 · Original practice · 1 mark
    Which functional group is present in the structure shown?
    Organic chemistry
11. Q18 · Original practice · 1 mark
    What is the IUPAC name of $\mathrm{CH_3CH(CH_3)CH_2CH_2OH}$?
    Organic chemistry
12. Q19 · Original practice · 1 mark
    Which compound can show cis–trans isomerism?
    Organic chemistry
13. Q20 · Original practice · 1 mark
    Which compound contains a chiral carbon?
    Organic chemistry
14. Q21 · Original practice · 1 mark
    Propene reacts with hydrogen bromide under conditions favouring the Markovnikov product. The major product is
    Organic chemistry
15. Q22 · Original practice · 1 mark
    Excess acidified potassium dichromate is heated under reflux with propan-1-ol. The principal organic product is
    Organic chemistry
16. Q23 · Original practice · 1 mark
    Which pair forms ethyl methanoate by esterification?
    Organic chemistry
17. Q24 · Original practice · 1 mark
    Compared with LDPE, HDPE generally has
    Polymers and biomolecules
18. Q25 · Original practice · 1 mark
    A tripeptide is formed from three amino-acid molecules. How many peptide bonds and water molecules are formed?
    Polymers and biomolecules
19. Q26 · Original practice · 1 mark
    An amino-acid spot travels 3.6 cm while the solvent front travels 6.0 cm from the baseline. Its $R_f$ is
    Organic analysis
20. Q27 · Original practice · 1 mark
    An amino acid with isoelectric point 6.0 undergoes electrophoresis at pH 3.0. Its net charge and direction of migration are
    Organic analysis
21. Q28 · Original practice · 1 mark
    A compound has a strong IR absorption near 1715 cm⁻¹ but no broad O–H absorption. Which class is consistent with this evidence?
    Organic analysis
22. Q29 · Original practice · 1 mark
    $\mathrm{N_2+3H_2\to2NH_3}$. A batch starts with 1.0 mol of nitrogen and 2.4 mol of hydrogen. The theoretical amount of ammonia is
    Chemical synthesis
23. Q30 · Original practice · 1 mark
    In an acidic hydrogen–oxygen fuel cell, which cathode half-equation is correct?
    Chemical synthesis
24. Q31 · Original practice · 4 marks
    A small sealed display vial contains brown $\mathrm{NO_2}$ and colourless $\mathrm{N_2O_4}$: $\mathrm{N_2O_4(g)\rightleftharpoons2NO_2(g)}$. The brown colour deepens when the vial is warmed.
    Chemical equilibrium