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Electronic configuration of Chromium: \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}\)

No expanded working has been attached for this question yet. The verified answer is Option C.

Each double bond has two pairs of valence electrons shared to form a covalent bonding. Also, every C-H bond, has 2 valence elctrons involved. Drawing the Lewis structure, you see that the above compound has 12 valence electrons shared.

The chlorine atom is much more electronegative than the hydrogen atom, which makes this bond polar.

In CO2, due to electronegativity difference oxygens have slight negative charge, hence surrounded by polar water molecule forming a cage structure.This leads to its solubility.

Every other factor influences the formation of elecrovalent or Ionic bonds except Catalytic ability.

Solids vibrate but generally do not move from place to place. The particles in solids vibrate back and forth around fixed positions. This motion is called vibrational motion.

(a)(i) Sketch of Graphical Representation of Charles' Law: Volume (cm\(^3\)) (ii) Volume of O\(_{2(g)}\) required for complete combustion of 2.5 moles of ethanol at s.t.p. \(C_2\)\(H_5\)OH\(_{(aq)}\) + 3O\(2_2\) -> 3\(H_2\)O + 2CO\(_{2(g)}\) 1 mole of ethanol = 3 x 22.4 dm\(^{2}\). of O\(_{2(g)}\) .-. 2.5 moles of ethanol = 3 x 22.4 dm\(^{3}\) x 2.5 = 168.0 dm\(^{3}\). (b)(i) Collision theory of reactants rates states that atoms/molecules/ions/particles/reactions involved in a chemical reaction must collide with effective collision before reaction can take place. (ii) Using collision theory to explain effect of temperature on the rate of a chemical reaction: Increase in temperature makes the reacting molecules to gain kinetic energy and move faster. Where the temperature decreases, the reacting molecules lose kinetice energy and move slower. Frequency of collision and effective collision increase or decrease, therefore rate of reaction increases or decreases. (c)(i) Esterification is the reaction between an alkanol and alkanoic acid to produce an Alkanoate (ester) and water in the presence of a mineral acid. (ii) Two uses of alkanoates are: (1) Used in perfumes/cosmetics. (2) Used in artificial flavouring for foods. (3) Used in production of soap. (4) Used as plasticizers. (Any 2) (iii) Products of the alkaline hydrolysis of ethyl ethanoate are: ethanol (\(C_2\)\(H_5\)OH) and sodium ethanoate (C\(H_3\)COONa) or potassium ethanoate C\(H_3\)COOK. (d)(i) Tin-coated plate corrodes faster. (ii) Zinc is more reactive than tin, higher in the electrochemical series than tin. When the tin coated plate is exposed, the plate goes into solution and corrodes. In zinc coated (galvanized) plate, it is zinc that dissolves and corrodes hence protecting the plate better and zinc coated plate does not corrode.

(a)(i) Structure of the sixth member of the alkenes: C\(_n\)H\(_{2n}\); n = 7, C\(_7\)H\(_{2 \times 7}\) = C\(_7\)H\(_14\) (Double can be positioned within any of the carbon chain) (ii) Relative molecular mass of the sixth member of alkene (C\(_7\)H\(_14\) \(\begin {bmatrix} C & = 12 \\ H & = 1 \end{bmatrix}\) (C\(_7\)H\(_14\) = (12 x 7) + (1 x 14) = (12 x 7) + (1 x 14) = 84 + 14 = 98 (no units) (iii) One differences between cracking and reforming in the petroleum industry: CRACKING REFORMING Involves breaking large molecules of petroleum fractions into smaller molecules Involves re-arrangement of atoms in molecules of petroleum fraction to obtain branched and cyclic hydrocarbons Used to improve the quantity of petrol. Used to improve the quality of petrol. Can be achieved thermally or catalytically Occurs in presence of a catalyst (b)(i) Enthalpy of neutralization is the beat evolved when an acid reacts with a base to form one mole of water or when one mole of OH\(^{+}\) from an acid reacts with one mole of OH\(^{-}\) from a base to form one mole of water. (ii) Determination of enthalpy of neutralization of the reaction of dilute hydrochloric acid and aqueous potassium hydroxide HCI\(_{(aq)}\)+ KOH\(_{(aq)}\) -> KC1 + \(H_2\)O Equimolar solutions of hydrochloric acid and potassium hydroxide are prepared separately. A known volume of the acid is placed in a calorimeter/polystyrene beaker and the temperature recorded. The same volume of the potassium hydroxide solution at the same temperature is poured into the calorimeter and the mixture stirred gently. The maximum temperature of the mixture is recorded. Heat lost in the reaction = heat gained by the solution formed OR \(\bigtriangleup\) H neutralization = mass of solution x specific heat capacity of water x change in temperature. (c) An electrochemical cell connected with copper and silver electrodes. (i) A node : copper electrode (ii) Cathode : silver electrode reasons in 3(c)(i) (iii) Silver has a more positive Standard electrode potential than copper. Copper is more electropositive than silver or copper is higher in the electrochemical series (iv) Type of reaction occuring at each electrode. Anode : oxidation (occurs at the copper electrode). Cathode : reduction (occurs at the silver electrode). (v) Balanced chemical equation for the overall cell reaction. Cu\(_s\) + 2Ag\(^+\) \(\to\) CU\(^{2+}_{(aq)}\) + 2Ag\(_(s)\) (d) Compound formed when iron is exposed to moist air for a long time; (i) Hydrated Iron(III) oxide. (ii) Balanced chemical equation for the reaction in 3(d)(i). 4Fe\(_s\) + 3O\(_{2(g)}\) + 2 x H\(_2\)O\(_l\) \(\to\) 2Fe\(_2\)O\(_3\).XH\(_2\)O where X is 1 4Fe\(_s\) + 3O\(_{2(g)}\) + 2H\(_2\)O\(_l\) \(\to\) 2Fe\(_2\)O\(_3\).H\(_2\)O (iii) One ore of iron: haematite, magnetite, siderite/spathic iron ore, limonite, iron pyrites

(a)(i) A labelled diagram for the laboratory preparation of a dry, sample of sulphur (iv) oxide. (Any one situable but must correspond to reactants in the diagram) (ii) Balanced chemical equation for the reaction in 4(a)(i) NaSO\(_{3(aq)}\) + 2HCl\(_{(aq)}\) —> 2NaCl\(_{3(aq)}\) H2O\(_{(l)}\) + SO\(_{2(g)}\) OR \(K_2\)SO\(_{3(aq)}\) + 2HCl\(_{(aq)}\) —> H\(_2\)\(O_l\) + SO\(_{2(g)}\) OR NaSO\(_{3(aq)}\) + H\(_2\)SO\(_{4(aq)}\) —> 2N\(a_2\)SO\(_4\) + H\(_2\)O\(_{(l)}\) + SO\(_{2(g)}\) (iii) Precaution in the preparation of the gas in 4(a)(i). The gas should be prepared in a fume cupboard (chamber). (iv) Reason for the precaution. It is because the gas is poisonous. (b)(i) Dalton's law of partial pressures states that for a mixture of gases which do not react, the total pressure is equal to the sum of the partial pressures of the individual gases. (ii) Volume of methane (CH\(_4\)) collected over water at temperature of 12^\circC and a pressure of 700mmHg was 30cm\(_3\). Volume of the gas (dry) at s.t.p. \(\frac{P_1V_1}{T_1} = \frac{P_2 V_2}{T_2}\) \(P_1\) = (700 — 10) = 690 mmHg (dry gas) \(T_1\) = 12 + 273 = 285 K \(V_2\) = \(\frac{P_1V_1T_2}{P_2T_1}\) P\(_2\) = 760mmHg, T\(_2\) = 273k \(V_2\) = \(\frac{690 \times 30 \times 273}{760 \times 285}\) \(V_2\) = 26.09cm\(^3\) \(V_2\) = 26.10cm\(^3\) (c)(i) Equation for the reaction between chlorine and water. Cl\(_{2(g)}\) + H\(_2\)O \(\to\) HCI + HCIO (ii) Litmus paper turned red (from blue to red) because H\(^+\) ions are released or HCI produced is acidic. Also HCIO produced is acidic too. The solution is acidic. (d)(i) Trend in the boiling points of chlorine, bromine and iodine. Boiling point of iodine is greater than that of bromine which is greater than that of chlorine. Boiling point increases from chlorine to iodine. (ii) Water has a higher boiling point than ammonia because water has stronger hydrogen bonds than ammonia. Also because oxygen atom has two lone pairs of electrons and nitrogen atom has one pair of electron. Also oxygen is more electronegative than nitrogen.

(a)(i) Two industrial uses of hydrogen: —filling of weather balloons. —manufacture of plastics. —manufacture of ammonia by the Haber process. —manufacture of methanol. —oil refinery process/hydrocracking —used in fuel cells. —manufacture of margarine. —in oxy-hydrogen flame (for welding and cutting metals). —as reducing agent in production of metals, e.g. Cu and.Pb from their oxides. —conversion of coal to crude oil. —(liquid) hydrogen is used as rocket fuel/gaseous fuel (Any 2). (ii) Mg(HCO\(_3\))\(_{2(aq)}\) —> MgCO\(_3\)\(_{(s)}\) + H\(_2\)O\(_{(l)}\) + Cu\(_3\). In the equation above: (1) the type of hardness of water being removed is temporary hardness of water. (2) two disadvantges of hardness of water are: —scales/furrinab of kettles/pipes causing blockage leading to power wastage. —soap is wasted not suitable for laundry. —not suitable for use in tanning, textiles and paper production (Any 2). (b)(i) Disadvatnages of using graphite electrodes in the extraction of aluminium by electrolysis: At high temperature oxygen gas produced at the anode reacts with the graphite electrodes to form carbon(IV) oxide. (ii) Balanced equation of reaction between calcium oxide and water to form slaked lime: CaO + H\(_2\)O \(\to\) Ca(OH)\(_2\) (iii) One use of slaked lime: —used to treat acidic soil. —used to make mortar/plasters/cement/hold bricks. —in manufacture of glass. —purification of water/removing hardness of water. —manufacture of white wash. —to test for CO\(_2\). —production of bleaching powder: —to recover or produce ammonia from ammonium chloride used in solvay process. (c)(i) Saponification is the alkaline hydrolysis of fats/oils to produce soap and propane —1,2,3-triol (ii) Raw materials needed for the manufacture of soap: —oil/fat. —alkali (1) (sodium hydroxide/potassium hydroxide (iii) Main by-product obtained from the manufacture of soap is propane —1,2,3-triol. (d) Extraction of iron in the blast furnace using iron-ore, coke and limestone as raw materials with the aid of chemical equations.. (i) Bottom of furnace: The O\(_2\) in the hot air combines with carbon(coke) to produce carbon (IV) oxide which is reduced to carbon (II) oxide. C + O\(_2\) \(\to\) CO\(_{2(g)}\) CO\(_{2(g)}\) + C \(\to\) 2CO\(_{(g)}\) (ii) Middle of the furnace: The calcium carbonate CaCO\(_3\) decomposes under great heat to form CO\(_2\) and CaO and CaCO\(_3\) decomposes to remove the impurities SiO\(_2\) CaCO\(_3\) —> CaO\(_s\) + CO\(_{2(g)}\) CaO + SiO\(_2\) --> CaSiO\(_3\). (iii) Top of furnace: Iron (III) oxide is reduced to metallic iron Fe\(_2\)O\(_2\) + 3CO 2Fe + 3CO\(_2\) OR Fe\(_3\)O\(_4\) + 4CO —> 3Fe + 4CO\(_2\).

(ai) Fermentation is the conversation of aqueous glucose or sugar to ethanol/alcohol and release of carbon (iv) oxide as a by product. Alternatively, it is the decomposition or breakdown of glucose/starch/carbohydrate to ethanol/alcohol and release of carbon (iv) oxide (aii) Zymase (b) -The strength of an acid -The PH of the solution (c) Fe + H\(_2\)SO\(_4\) -> FeSO\(_4\) + H2 mass of unreacted iron calculated below; No. of moles of H\(_2\)SO\(_4\) = 10cm\(^3\) Concentration = 1mol/dm\(^3\) Amount = Vol x Concentration = \(\frac{10}{100}\) x 1 = 0.01mol 1 mole of H\(_2\)SO\(_4\) = 1 mole of Fe Mass of Fe reacted = 56 x 0.01g = 0.56g Mass of unreacted Fe = (5.0 - 0.056)g = 4.44g (di) tetraoxsulphate (iv) (dii). dyes (e) A catalyst increases the rate of reaction by lowering the activation energy of the reaction (fi) CH\(_3\)COOH\(_{(s)}\) + NH3\(_{(g)}\) → CH\(_3\)COONH\(_4\) (fii) Ammonium ethanoate (g) (a) It doesn’t corrode easily. (b) it doesn’t react with contain inside. (c) It can stand for a long period of time. (h) (a) Sweet production industries (b) perfume industries. (i) (a) Evaporation (b)seedling (j) (a) it increases the volume water in ocean and seas. (b) It causes increase in rainfall and also corrode painted surfaces

This is a popular question among the candidates. In part (a), majority of the candidates listed the two gaseous fuels produced from coke. In part (b), majority of the candidates could not differentiate between thermosets and thermoplastics. They could not give one example thermosets and thermoplastics. In part (c), majority of the candidates stated the method of collecting gases which are denser than air. Also, majority of them named two gases that could be used to perform the fountain experiment in the laboratory. In part (d), majority of the candidates stated two compounds that could be used to test for water. They gave three disadvantages of hard water. The expected answers include: (a)(i) - producer gas -water gas (ii) Water gas (iii) It is because producer gas contains about 67% / more non-combustible nitrogen and 33% / less of combustible carbon (II) oxide while water gas consist of equal amounts of combustible carbon (II) oxide and hydrogen. (iv) - 2C(s) + O\(_2\) + 4N\(_2\) → 2CO + 4N\(_2\) - C(s) + H\(_2\)O(g) → CO(g) + H\(_2\)(g) (b)(i) Thermoplastics can be softened by heat and remoulded while thermosets cannot be softened by heat and remoulded once they are formed or set. (ii) Examples: Thermosets: Urea-methanal Polyvinyl chloride (p.v.c.) Bakelite Thermoplastics: Polyethene Polypropene/ Polyamide Nylon Perspex Polystyrene Terylene (iii)- good insulators - can be recycled/softened and reshaped - are non-biodegradable - can be tailor – made to exact requirements - resistance to corrosion - water-proof (c)(i) Upward displacement of air / downward delivery (ii) - hydrogen chloride - ammonia - sulphur (IV) oxide (iii) The gases are highly/very soluble in water. (d)(i) - copper (II) tetraoxosulphate (VI)/CuSO\(_4\) - cobalt (II) chloride/CoCl\(_2\) (ii) - wastes soap/forms scum/costs a lot of money to soften/does not readily lather with soap - causes furring/scales in kettles / boilers - cannot be used in dyeing / tanning

(a) A compound is defined as a substance containing two or more elements / different atoms chemically combined (in a fixed proportion by mass) (b) - high temperature - catalyst - high pressure (c)- Iron - Nickel - Palladium - Platinium - Rhodium (d)(i) Zn(s) + 2AgNO\(_3\)(aq) → Zn(NO\(_3\))\(_{2(aq)}\) + 2 Ag(s) (ii) I. AgNO\(_3\) / Ag + is reduced II. Zn is oxidized (e) \(\frac{16}{8}\)O = 90%, \(\frac{18}{8}\)O = 10% Relative atomic mass = \(\frac{\frac{16 \times 90}{199} + \frac{18 \times 10}{100} }{(16 \times 0.9) + (18 \times 0.1)}\) = \(\frac{1440}{100} + \frac{180}{100}\) = 14.4 + 1.8 = 16.2 (f) - haematite (Fe\(_2\)O\(_3\))/ Iron (III) oxide - magnetite (Fe\(_3\)O\(_4\))/Iron (II) Iron (III) oxide - limonite Fe\(_2\)O\(_3\).nH\(_2\)O/Iron (III) oxide hydrate(accept FeO(OH).nH\(_2\)O) - iron pyrites FeS/Iron (II) Sulphide - Siderite/spathic iron ore /FeCO\(_3\)/Iron (II) trioxocarbonate (IV) (g) (i) It is the use of biological processes / organisms / system to manufacture useful products (ii) - garri, fufu, kenkey, bread - bio-gas, - alcoholic beverages (beer, whisky, burukutu, gin, etc) - drugs (vaccines, hormonal, antibiotics) - enzymes - biodegradable plastics - pests control - organic fertilizers (h) An element is defined as a substance containing only one type of atom / substance which cannot be broken down into a simpler one. (i) - land fill sites / compost - marshes/swampy area - rice (paddy) fields - bacteria - natural gas - biomass burning - crude oil/petroleum - decay of organic matter - raising of livestock - coal mine (j) The molecules are held together by van der Waal’s forces . The larger the atom, the greater the van der Waal’s forces/increase in molecular mass and hence the higher the boiling point.

(a) When a standard hydrogen electrode is connected to a standard zinc half-cell the emf measured is 0.76V. The negative sign implies the flow of electrons from the zinc electrode to the hydrogen electrode. (b)(i) Anode/ Zn electrode Zn(s) → Zn\(^{2+}\)\(_{(aq)}\) + 2e\(^-\) / Zn(s) – 2e\(^-\) → Zn\(^{2+}\)\(_{(aq)}\) Cathode/Cu electrode Cu\(^{2+}\) \(_{(aq)}\) + 2e\(^-\) → Cu(s) (ii) Zn(s) + Cu\(^{2+}_{(aq)}\) → Zn\(^{2+}_{(aq)}\) + Cu(s) (iii) Anode/Zn electrode – oxidation Cathode/Cu electrode – reduction (iv) Eocell = Eored – Eooxid = (0.34 V) – (-0.76 V) = + 1.10 V (c) (i) - Textile - Brewery - Plastic - Refinery - Cement - Food [e.g flour, tea, sugar, etc] - Pharmaceutical - Fertilizer - Metallurgical - Paint - Soap and detergent - Ceramic - Rubber - Glass - Etc (ii) - nearness to raw materials / feed stock - nearness to market - labour supply - transportation - nearness to power supply - government policy - away from residential area - availability of water (iii)- Improvement in the standard of living - Employment opportunities - Development in the community - Pollution: air, noise, water, thermal - Social effects (d)(i) Hydrogen peroxide reduces silver oxide to silver metal/H2O2is oxidized to O2 A + H\(_2\)O\(_2\)\(_{(aq)}\) → 2Ag\(_{(s)}\) + H\(_2\)O\(_{(l)}\) + O\(_{2(g)}\) (ii) Hydrogen peroxide reduces chlorine to hydrochloric acid/H\(_2\)O\(_2\) is oxidized to O\(_2\) Cl\(_{2(g)}\) + H\(_2\)O\(_{2(aq)}\) → 2HCl\(_{(aq)}\) + O\(_{2(g)}\) (e) - colourless - odourless - slightly lighter / less dense than air - slightly soluble in water - low melting (-210\(^{o}\)C/ 63 K)/low boiling point (-196\(^{o}\)C/ 77 K)