(a) - high temperatures / stated temperature of 500\(^o\)C or more
- catalyst
(b) - To prevent corrosion/rusting/tarnishing
- To make them shiny/for decoration purpose/beautify/attractive
- To make surface harder/thicker
- To make more resistant to chemicals
- To make it durable
- To reduce friction/abrasion


(c) (i) Because calcium oxide is basic and hydrogen chloride is acidic ,they will react
to form salt and water.

(ii) - Fused CaCl\(_2\)
- (Conc) H\(_2\)SO\(_4\) (do not accept dil H\(_2\)SO\(_4\))
- Silica gel
- Phosphorus(V) oxide/P\(_2\)O\(_5\)

(d) Conc. HNO\(_3\) is a strong oxidizing agent. It oxidizes pale green Fe\(^{2+}\) ions to yellow Fe\(^{3+}\) ions (1) and itself reduced to nitrogen (IV) oxide.

(e) (i) I. ZnO(s) + H\(_2\)SO\(_{4(aq)}\) \(\to\) ZnSO\(_{4(aq)}\) + H\(_2\)O\(_{(l)}\)
II. ZnO\(_{(s)}\) + 2NaOH\(_{(aq)}\) \(\to\) Na\(_{2}\) Zn(OH)\(_{4 (aq)}\)

OR
ZnO + 2NaOH \(\to\) Na\(_2\)ZnO\(_2\) + H\(_2\)O
(ii) Amphoterism / Amphoteric properties
(f) (i) Same number (17) of protons / same number (17) of electrons/same atomic number
(ii) Difference in mass numbers / different number of neutrons / 35Cl has 18 neutrons and 37Cl has 20 neutrons
(g) - HCl / hydrochloric acid
- O\(_2\) / Oxygen

(h) (i) H\(_2\)S
(ii) SO\(_2\)

(i) It is the mass reference scale in which the atom of the 12C isotope is taken to have twelve units of atomic mass OR It is a scale that uses the 12C isotope as the standard for comparing the atomic masses of other elements.
(j) - The rate of forward reaction equals the rate of backward reaction / The system is dynamic
- There is no net change in the concentration of each substance
- The equilibrium compositions of the substances can be approached from either reactants or products
- Gibb’s free energy/ is zero