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 12 of 16

1. Q56 · Original practice · 4 marks
   Molten aluminium oxide is electrolysed. Aluminium ions require three electrons per atom. A laboratory cell produces 2.70 g of Al at 5.00 A with 100% current efficiency. Use $M(\mathrm{Al})=27.0\ \mathrm{g\,mol^{-1}}$ and $F=96485\ \mathrm{C\,mol^{-1}}$.
   Redox and electrochemistry
2. Q57 · Original practice · 5 marks
   A hydrogen–oxygen fuel cell operates in alkaline electrolyte.
   Chemical synthesis
3. Q58 · Original practice · 4 marks
   Vanadium(V) oxide, $\mathrm{V_2O_5}$, is reduced to $\mathrm{V^{3+}}$ in acidic solution.
   Redox and electrochemistry
4. Q59 · Original practice · 5 marks
   A liquid contains 60.0% carbon, 13.3% hydrogen and 26.7% oxygen by mass. Its molar mass is approximately 60.0 g mol⁻¹. Use atomic masses C = 12.0, H = 1.00, O = 16.0.
   Organic chemistry
5. Q60 · Original practice · 4 marks
   The graph gives approximate normal boiling points of the first five straight-chain primary alcohols.
   Organic chemistry
6. Q61 · Original practice · 5 marks
   Three non-cyclic alkane structures share the formula $\mathrm{C_5H_{12}}$.
   Organic chemistry
7. Q62 · Original practice · 4 marks
   The structures show two isomers of 1,2-dichloroethene.
   Organic chemistry
8. Q63 · Original practice · 3 marks
   The displayed molecule is 2-bromobutane.
   Organic chemistry
9. Q64 · Original practice · 5 marks
   A two-step pathway converts but-1-ene into butan-2-one.
   Organic chemistry
10. Q65 · Original practice · 4 marks
    Three unlabelled vials contain hexane, hex-1-ene and hexan-1-ol. Small samples may be tested separately.
    Organic chemistry
11. Q66 · Original practice · 4 marks
    Separate samples of butan-1-ol, butan-2-ol and 2-methylpropan-2-ol are heated with excess acidified potassium dichromate.
    Organic chemistry
12. Q67 · Original practice · 4 marks
    Ethyl propanoate is warmed with dilute acid and excess water.
    Organic chemistry
13. Q68 · Original practice · 5 marks
    Butan-1-ol and butan-2-one have similar molar masses but boiling points of approximately 118 °C and 80 °C respectively.
    Organic chemistry
14. Q69 · Original practice · 4 marks
    Glycine has the neutral structural formula $\mathrm{H_2NCH_2COOH}$.
    Polymers and biomolecules
15. Q70 · Original practice · 5 marks
    Use glycine $\mathrm{H_2NCH_2COOH}$, alanine $\mathrm{H_2NCH(CH_3)COOH}$ and serine $\mathrm{H_2NCH(CH_2OH)COOH}$ to form the tripeptide Gly–Ala–Ser.
    Polymers and biomolecules
16. Q71 · Original practice · 4 marks
    Two glucose molecules, each $\mathrm{C_6H_{12}O_6}$, join to form the disaccharide maltose.
    Polymers and biomolecules
17. Q72 · Original practice · 4 marks
    The two displayed monomers are used to make nylon-6,6.
    Polymers and biomolecules
18. Q73 · Original practice · 3 marks
    Poly(lactic acid), PLA, has ester links in its backbone. Polyethene has a carbon–carbon backbone.
    Polymers and biomolecules
19. Q74 · Original practice · 4 marks
    Two polypropene samples have identical chain lengths. In X, methyl groups follow a regular isotactic arrangement. In Y, they follow an irregular atactic arrangement.
    Polymers and biomolecules
20. Q75 · Original practice · 4 marks
    A TLC plate compares amino-acid standards G and A with a mixture. The solvent front travels 8.0 cm. The lower and upper spots travel 2.4 cm and 4.8 cm respectively. Standards and mixture are run under identical conditions.
    Organic analysis
21. Q76 · Original practice · 4 marks
    The illustrative IR spectrum belongs to one of these compound classes: alkane, alcohol, ketone or carboxylic acid.
    Organic analysis
22. Q77 · Original practice · 4 marks
    A spectrum has a molecular ion at $m/z=58$ and a base peak at $m/z=43$. The two candidates are propanal and propanone. The 43 fragment is assigned as $\mathrm{CH_3CO^+}$.
    Organic analysis
23. Q78 · Original practice · 5 marks
    A compound contains 54.5% C, 9.1% H and 36.4% O by mass. Its molecular-ion peak is at $m/z=88$ (singly charged). The IR spectrum has a strong carbonyl band and a broad acid O–H band. Use C = 12.0, H = 1.0, O = 16.0.
    Organic analysis
24. Q79 · Original practice · 4 marks
    A purified amino acid with isoelectric point 5.8 is placed at the origin of the electrophoresis apparatus. The buffer has pH 8.0.
    Organic analysis