• The University of Hong Kong

• HKDSE CHEM1000

CHEMISTRY

S4 Final Term Exam

HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION

CHEMISTRY

(SECONDARY FOUR FINAL TERM

EXAMINATION PAPER)

Suggested Answers

Section A

Explanation

1. Ammonia, chlorine and nitrogen dioxide are all soluble in water. They cannot be collected by

displacement of water.

2. Option (A): All Group I elements have one electron in the outermost shell.

Option (C): The number of neutrons of an atom cannot be deduced from the position of the

element in the Periodic Table.

3. Option (A): Mg(s) + 2H2O(l) ® Mg(OH)2(s) + H2(g)

Option (B): Ca(s) + 2HCl(aq) ® CaCl2(aq) + H2(g)

Option (C): Metals lower than lead in the reactivity series (e.g. copper and silver) do not react

with dilute sulphuric acid.

Option (D): Zn(s) + H2O(g) ® ZnO(s) + H2(g)

HKDSE CHEMISTRY — A Modern View (Second Edition) S4 Final Term Exam

© Aristo Educational Press Ltd 2021 A1

CHEMISTRY

S4 Final Term Exam

4. C12H26 ® 2C2H4 + C8H18

5. The electronic arrangement of an atom of X is 2, 6. Hence, an X atom shares two outermost

shell electrons with another X atom to form a stable X2 molecule.

6. The chemical formulae of lithium bromide, calcium chloride, silicon dioxide and sodium oxide

are LiBr, CaCl2, SiO2 and Na2O respectively. SiO2 is a covalent compound.

7. Option (A): A dirty green precipitate is produced: Fe2+(aq) + 2OH-(aq) ® Fe(OH)2(s)

Option (B): A reddish brown precipitate is produced: Fe3+(aq) + 3OH-(aq) ® Fe(OH)3(s)

Option (C): No precipitate is produced.

Option (D): A white precipitate is produced: Al3+(aq) + 3OH-(aq) ® Al(OH)3(s)

9. Iron(II) ions produced during rusting turns potassium hexacyanoferrate(III) blue.

10. In Tubes 1 and 2, the iron nails do not rust. Since magnesium and zinc are more reactive than

iron, they lose electrons more readily than iron.