(i) Name two amorphous forms of carbon
(ii) State the reason why graphite is a lubricant but diamond is not.
(iii) Draw and label a diagram for the laboratory preparation of a dry sample of carbon (IV) oxide.
(b)(i) Give one example of the following: I. Soil pollutant; II. Water pollutant; III. Air pollutant.
(ii) State the major use of sulphur (IV) oxide in a chemical industry.
(c)(i) Explain in terms of the kinetic theory why petrol is volatile
(ii) State two criteria for determining the purity of a substance.
(iii) Mention one use of each of the following gases: I. Krypton; II. Argon
(d)(i) When zinc metal was added to aqueous copper (I) tetraoxosulphate (VI), the solution turned colourless. I. Name the compound in the colourless solution. II. Write the ionic equation for the reaction. Ill. State what would be observed when a few drops of sodium hydroxide solution is added to a portion of the colourless solution.
(ii) Calculate the volume of CO\(_2\) produced when 5.3g of Na\(_2\)CO\(_3\) reacted with excess HNO\(_{3(aq)}\) + Na\(_2\)CO\(_3\) + 2HNO\(_{3(aq)}\) \(\to\) 2NaNO\(_{3(aq)}\) + CO\(_{2(g)}\) + H\(_2\)O\(_{(l)}\) [H = 1, C = 12, N = 14, O = 16, Na = 23, 1 mole of a gas occupies 22.4 dm\(^3\) at s.t.p.]
Explanation
(i) Coke, Coal, Carbon black, any of the charcoal and carbon fibers.
(ii) Graphite is a lubricant because of its layered crystalline structure which allows one layer to slide over one another while diamond has ;table and rigid crystal lattice.
(iii) Draw the diagram on the marking scheme.
(b)(I) Soil pollutant iomestic waste, polythene, pesticides, oil spillage, etc.
(II) Water pollutant — Factory waste, domestic waste etc.
(III)Air pollutant — Sulphur (IV) oxide, carbon (II) oxide, oxides of nitrogen and chlorofluorocarbon, etc.
(ii) The major use of SO\(_2\) in a chemical industry is in the manufacture of H\(_2\)SO\(_4\).
(c)(i) The intermolecular orces in petrol are weak and hence are easily broken for the molecules to escape.
(ii) The criteria are ponstant melting point, constant boiling point, its density, refractive index, etc.
(iii) Krypton is used in photography, etc.
(ii) Argon is used in gas-filled electric lamps.
(d)(i) I. Zinc tetraoxosulphate (VI) ; Zn\(_{(s)}\) + Cu\(^{2+}\)SO\(^{2-}_{4}\) --> Zn\(^{2+}\) + Cu\(_{(s)}\)
OR Zn\(_{(s)}\) + Cu\(^{2+}_{(aq)}\) --> Zn\(^{2+}_{(aq)}\) + Cu\(_{(s)}\)
IIl. A white precipitate is Formed
(ii) Na\(_2\)CO\(_{3(s)}\) + 2HNO\(_{3(aq)}\) ---> 2NaNO\(_{3(aq)}\) + CO\(_{2(s)}\) + H\(_2\)O\(_{(l)}\)
Molar mass of Na\(_2\)CO\(_3\) = 23 + 2 + 12 + 16 x 2 = 106.
106 of Na\(_2\)CO\(_3\) produces 22.4dm\(^3\) of CO\(_2\) at s.t.p.
5.3g of Na\(_2\)CO\(_3\) will produce \(\frac{5.3 \times 22.4}{106}\)
= 1.12 dm\(^3\)