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Oxalic acid - HOOCCOOH It is the simplest dicarboxylic acid. It is a white crystaline solid that forms a colorless solution in water.

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- The presence of impurities in a substance results in a lower melting point due to a process called melting point depression. - That implies a pure solid has a SHARP melting point which is of the standard value when compared.

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Nitric oxide is an important component of the air pollution generated by automotive engines and thermal power-generating plants. sulphur dioxide may also be produced in case of fuel containing sulphur, Nigeria crude is sulphur free,

(a)(i) Ionic bond is the electrostatic force of attraction between oppositely charged ions/cations and anions. OR Ionic bond is defined as the type of bond that is formed from/ by/ through the transfer of electrons from one atom of an element (metal) to an atom of another (non - metal). (ii) (I) – Ionic / electrovalent. (II) – „Coordinate (Covalent) / dative. (b) Oxidation number of sulphur in Na\(_2\)S\(_2\)O\(_2\); 2 x Na + 2 x S + 3 x 0 = 0 2 x 1 + 2s + 3(-2) = 0 2 + 2s – 6 = 0 2s = 4 s = +2 c) Farady's first law states that the mass of an element discharged during electrolysis is directly proportional to the of current passed. (d)(i) NaHSO\(_4\), NaHCO\(_3\), KHSO\(_3\), etc. (ii) Mg(OH)Cl, Zn(OH)Cl, Zn(OH)NO\(_3\), etc. e)(i) Sublimation energy. (ii) Electron affinity. f) (i) Na\(_2\)SO\(_{4(aq)}\) No effect on litmus paper/Neutral to litmus. (ii) AlCl\(_{3(aq)}\) —Turns blue litmus paper red/Acidic to litmus. (g) Efflorescence: Loss of (all apart from) water of crystallization by a substance on exposure to the air/Atmosphere. (h) Activated Charcoal: (i) To remove colouring matter. (ii) To absorb gases. (iii) To remove impurities from liquids. (iv) Whitening of teeth. (v) To remove scent/To decolourize. (i)(i) Hydrogenaton of Vegetable Oil: Production of margarine/Hardening of oils. (ii) Cracking: Increase the yield of petrol/Improves the quality of petrol to produce raw materials or petrochemicals. (iii) Esterification: Production of akanoates. —as solvents for paints/gums/cellulose. —in perfumery. —in making cellulose acetate (for photographic films). —as flavouring agents. j) Ag\(^{-}\) + eg\(^{-}\) \(\to\) Ag 96500c of electricity deposits I mole of Ag 10920c of electricity = \(\frac{10920 \times 1.0}{96500}\) = 0.113moles = 0.11 moles.

a)(i) Ion: (Electrically) charged atom or group of atoms formed from an atom by loss or gain of electron. (ii) Isotopes: Atoms of the same element with the same number of protons but different number of neutrons/Mass number (b)(i) I. \(_{(12)}\)Mg — 1s\(^2\)2s\(^2\)2p\(^6\)3s\(^2\) \(_{(13)}\)Al — 1s\(^2\)2s\(^2\)2p\(^6\)3s\(^2\)3p\(^1\) II. The 3p electron in Aluminium is slightly further away from the nucleus than the 3s electron of magnesium. The shielding / screening effect by the inner electrons is more in Al than in Mg. These two effects outweigh the increase in nuclear charge of Al, hence nuclear attraction for 3s is greater than the 3p. OR The 3s outermost orbital in Mg is fully filled and is therefore more stable than the 3p orbital in Al which is neither completely filled nor half-filled and, hence less stable. OR 3s orbital of Mg is close to the nucleus than the 3p orbital of Al, hence the nuclear attraction for the 3s is greater than the 3p. (ii) Na\(_2\)O, MgO, P\(_4\)O\(_{(10)}\), SO\(_3\), CI\(_2\)O\(_7\), SO\(_2\), Na\(_2\)O\(_2\) (c)(i) Allotropes are different forms of the same element in the same physical state. (ii) Diamond and graphite. (iii) Diamond —For making jewellery. —For cutting hardly surface materials. —Making abrassives (ii) Graphite —As a lubricant. —For making pencals. —For making electrodes. —Neutron moderator. —Making crucibles. d)(i) —Colourless. —Has choking smell. —Denser than air. —Fumes in moist air. —Soluble in water. (ii) 2NaCl + H\(_2\)SO\(_4\) --> Na\(_2\)SO\(_4\) + 2HCl OR NaCl + H\(_2\)SO\(_4\) \(\to\) NaHSO\(_4\) + HCl e) Mass of W = 5.68mg = 5.68 x 10\(^{-3}\)g Moles of W = \(\frac{5.68 x 10^3}{28}\) = 2.03 x 10\(^{-4}\) moles

(i) (1) Aeration/exposure to sunlight. (2) Add alum/coagulation /flocculation. (3) Sedimentation. (4) Fi!teration. (5) Add chlorine /disinfectant. (6) Add flouride/iodide. (7) Add Ca(OH)\(_2\) / pH control. (ii) Cations that can cause hardness in water: Mg, Ca, Fe. (iii)Disadvantages of Hardness of Water: (1) It wastes soap. (2) Forms stain on white clothing and material (3) Forms boiler scale and kettle fur / damage. (4) It is unsuitable for industrial processes, e.g. dyeing and tanning. (iv) Sources of Water Pollution: (1) Wastes from industries, e.g. brewery. (2) Agricultural activities, e.g. fertilizer. (3) Waste from quarry activities. (4) Refuse from plant and animal origin. (5) Sewage (industrial and domestic). (6) Oil spillage. (b)(i) Water is a polar solvent and can therefore easily dissolve sodium chloride which is ionic / polar salt. Oil, on the other hand, is non-polar and, hence cannot dissolve in water which is polar. (ii) - H\(_2\)SO\(_4\) - As a dehydrating agent. - H\(_2\)SO\(_2\) - As an acid. - H\(_2\)SO\(_4\) As an oxidizing agent. (c)(i) HCl and O\(_2\) (ii)(I) Na\(_2\)CO\(_3\) (II) Na\(_2\)CO\(_3\) is stable in air and can be weighed accurately. NaOH absorbs water / deliquescent and cannot be weighed accurately.

(a)(i) I. Anode – Electrode at which oxidation occurs / electron loss II. Cathode – Electrode at which reduction occurs / electron gain (ii) I. Cathodic reaction Na\(^{+_(l)}\) + e\(^{-}\) —> N\(a_s\) . Anodic reaction 2cl\(^{-_(l)}\) --> C\(l_2\) + 2e\(^{-}\) II. Cathodic reaction Al\(^{3+}_{(l)}\) + 3\(^{-}\) —> Al. Anodic reaction 2O\(^{2-}_{l}\) ----> O\(_2\) + 4e\(^{-}\) (iii) In the extraction of aluminium, Oxygen is produced whereas in the extraction of sodium, chlorine is produced. Chlorine is an environmental pollutant whereas oxygen is not. (b)(i) The reaction is a redox because both oxidation and reduction occur simultaneously. The oxidation number of Cr changes from +6 (in K\(_2\)Cr\(_2\)O\(_7\)) to +3 (in CrCl\(_3\)). Cr is therefore reduced. The oxidation number of Cl changes from –1 (in HCl) to 0 (in Cl\(_2\)). CI is therefore oxidized. OR Removal of hydrogen from HCl is Oxidation. Removal of Oxygen from K\(_2\)Cr\(_2\)O\(_7\) is reduction. (ii) Reduction Cr\(_2\)O\(_2\)\(^{2-}\) + 14H\(^{+}\) + 6e\(^{-}\) \(\to\) 2Cr\(^{3+}\) + 7H\(_2\)O Oxidation 2Cl\(^{-}\) \(\to\) Cl\(_2\) + 2e\(^{-}\) (iii) Cr\(_2\)O\(_7\)\(^{2-}\) + 14H\(^{+}\) + 6Cl\(^{-}\) --> 2Cr\(^{3+}\) + 7H\(_2\)O + 3Cl\(_2\) OR K\(_2\)Cr\(_2\)O\(_7\) + 14HCl \(\to\) 2KCl + CrCl\(_3\) + H\(_2\)O + CI\(_2\) (c) Q = I x T 6 x (30 +60) x 60 = 32400C Al\(^{3+}\) + 3e\(^{-}\) \(\to\) Al\(_{(l)}\)