Question Library

(a) - addition of alum / addition of coagulating agent - sedimentation - filtration - disinfection / chlorination / addition of chlorine (b) (i) - iron (III) oxide - silicon (IV) oxide / sand - trioxosilicates (IV) (ii) because aluminium oxide has too high a melting point to eletrolyse on its own / bauxite has low silica content (iii) - Alumina and molten cryolite Melted and electrolysed Cell with carbon electrodes Molten aluminium produced at the base of cell. siphoned off / removed at the base (c) (i) A fine chemical industry is the one that manufactures chemicals in smaller quantities / amounts for specific use with high level of purity (ii) Fine chemical Heavy chemical - they are produced in smaller quantities - they are produced in larger quantities - they are highly pure - they are not pure - they are final products - they are intermediate products - they are more costly / expensive - less costly / less expensive (d) (i) C\(_{(s)}\) + O\(_{2(g)}\) (ii) Amount of coal burnt = \(\frac{5.4}{12}\) mol\(^{-1}\) = 0.45mol From the equation of the reaction moles of O\(_2\) used = moles of C burnt = 0.45 1 moles of O\(_2\) = 22.4 dm\(^3\) 0.45 mol O\(_2\) = 22.4 x 0.45 = 10.1dm\(^3\) (e) - platinum - carbon

(a) (i) - sulphur (IV) oxide /SO\(_2\) - nitrogen (IV) oxide / NO\(_2\) - nitrogen (II) oxide / NO - carbon (II) oxide / (CO) - methane / CH\(_4\) (ii) Large lumps have smaller surface area to volume ratio than the broken pieces which has a greater surface area / increased exposed surface area. This makes the broken pieces to collide more frequently. OR The greater the rate of frequency of successful collisions, the greater the rate of reaction hence for the pieces of coal more reactant particles are exposed at the surface thereby increasing the frequency of successful collisions between reactant particles. (iii) methane gas / CH\(_4\) (iv) coke / carbon (b) (i) - chlorine dioxide / (ClO\(_2\)) - sulphur (IV) oxide SO\(_2\) - hydrogen peroxide / H\(_2\)O\(_2\) - sodium peroxide Na\(_2\)O\(_2\) (ii) - Manganese (IV) oxide / MnO\(_2\) - Lead (IV) oxide / PbO2\(_2\) (iii) - CaO - MgO - Na\(_2\)O - K\(_2\)O (iv) Aluminium oxide (Al\(_2\)O\(_3\)), ZnO, PbO, SnO\(_2\), SnO, PbO\(_2\) (v) - nitrogen (IV) oxide / NO2\(_2\) (c) (i) (ii) Redox reaction (iii) Because Iron (II) ions is oxidized to iron (III) ions / chlorine is reduced to chloride ions / chlorine gas oxidizes iron (II) ions to iron (III) ions and in the process chlorine is reduced to chloride ions / oxidation number of iron increases from +2 to +3 while that of chlorine decreases from 0 to -1. (d) (i) A - delivery tube B - Calcium oxide / CaO / quicklime (ii) (iii) Ammonia (iv) To prevent the (round bottom) flask from cracking / to prevent the water / steam formed from condensing into the hot glass flask. (v) (I) Drying agent / To dry the gas (II) Upward delivery / downward displacement of air (e) - Paraffin wax - Asphalt / bitumen

Rough Tree 1st Titre 2rd Titre 3rd Titre Final reading cm\(^3\) 15.60 31.10 45.50 15.60 Initial reading cm\(^3\) 0.00 15.60 31.10 0.00 Volume of the acid cm\(^3\) 15.50 15.50 15.40 15.60 (a) Average Titre = \(\frac{15.50 + 15.40 + 15.60}{3}\) cm\(^3\) = \(\frac{46.50}{3}\)cm\(^3\) = 15.50 cm\(^3\) (b)(i) Concentration of B in moldm\(^{-3}\) 250cm\(^3\) of B contains 480g of FeCl\(_2\) 100 cm\(^{-3}\) of B will contain \(\frac{4.80}{250}\) x 1000g = 19.2 gdm\(^{-3}\) Concentration of B in moldm\(^{-3}\) ? = \(\frac{\text{conc. in gdm}^{-3}}{\text{molar mass}} = \frac{19.2 gdm^{-3}}{127 gmol^{-1}}\) = 0.151 mol dm\(^3\) Concentration of A in mol dm\(^{-3}\) = ? \(\frac{C_AV_A}{C_BV_B} = \frac{n_A}{n_B}\) C\(_A\) = Molar concentration in moldm\(^{-3}\) of KMnO\(_4\) = ? V\(_A\) = Volume of KMnO\(_4\) used = 15.50cm\(^3\) n\(_A\) = 1 C\(_B\) = Molar concentration of FeCl\(_{2(aq)}\) = 0.151 moldm\(^{-3}\) V\(_B\) = Volume of FeCl\(_{2(aq)}\) = 25.00 cm\(^3\) = \(\frac{C_A \times 15.50 cm^3}{0.151 mold dm^{-3} \times 25.00 cm^3}\) = \(\frac{1}{5}\) C\(_A = \frac{0.151 \times 1 \times 25.00}{5 times 15.50} = \frac{3.775}{77.50}\) = 0.0487 (3sf) C\(_A\) = 0.0487 moldm\(^{-3}\) (ii) Number of moles of Fe\(^{2+}\) in the volume of B pipetted? 1000 cm\(^3\) of B contains 0.151 moles of Fe\(^{2+}\) 25cm of B will contain \(\frac{0.151}{1000} \times 25\) moles = 0.0003775 mole of Fe\(^{2+}\)

TEST OBSERVATION INTERFERENCE (a) Sample C + distilled water + shaking Resulting solution + litmus paper Sample C dissolved to form a blue/greenish solution Solution turns blue litmus paper red Solution is acidic (I) 1st portion + NaOH\(_{(aq)}\) in drops Then in excess Blue precipitate formed Precipitate insoluble in excess Cu\(^{2+}\) is present (ii) 2nd portion NH\(_4\)OH\(_{(aq)}\) in drops Then in excess Light blue precipitate formed Precipitate dissolve in excess to form a deep blue solution Cu\(^{2+}\) is confirmed (iii) 3rd portion + AgNO\(_{3(aq)}\)+ NCl\(_{(aq)}\) White precipitate formed Precipitate insoluble Cl\(^{-1}\) or CO\(_{3^{2-}}\) or S\(^{2-}\) or SO\(_3^2\) Cl\(^{2-}\) is present (b)(i) Sample D + distilled water touching or feeling the test tubes Sample D dissolved to form a colourless solution Test tube feels cold on touching Dissolution is endothermic (ii) D\(_{(aq)}\) = HCl\(_{(aq)}\) Effervescence (bubbling) occurs, a colourless, odourless gad evolved Gas turned lime water milky CO\(_{2(g)}\) from CO\(_{3^{2-}}\) or HCO\(_3^-\)

(a) Observation made when 2cm\(^3\) of bench H\(_2\)SO\(_4\) was added to 2cm\(^3\) of barium chloride solution. H\(_2\)SO\(_{4(q)}\) + BaCl\(_{2(aq)}\) \(\to\) BaSO\(_{4(s)}\)(white) + 2HCl\(_{(aq)}\) White precipitate of BaSO\(_4\) Barium tetraoxosulphate(VI) is formed (b) Observation made by the addition of dilute hydrochloric acid to 1g of powered iron (III) sulphide (FeS) 2HCl\(_{(aq)}\) + FeS\(_{(s)}\) \(\to\) FeCl\(_{(aq)}\) + H\(_2\)S\(_{(g)}\) Effervescence (bubbling) occurs or evolution of a gas with a smell of rotten eggs and a green solution is formed. (c) Observation made by the addition of 2cm\(^3\) of dillute hydrochloric acid to 1g of iron filings and allowed to stand for sometime Effervescence or evolution of colourless, odourless gas noticed with the formation of light green solution that will turn brown after sometime.

CFCs (Chlorofluorocarbons) have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time

(a) Observation made when 2cm\(^3\) of bench H\(_2\)SO\(_4\) was added to 2cm\(^3\) of barium chloride solution. H\(_2\)SO\(_{4(q)}\) + BaCl\(_{2(aq)}\) \(\to\) BaSO\(_{4(s)}\)(white) + 2HCl\(_{(aq)}\) White precipitate of BaSO\(_4\) Barium tetraoxosulphate(VI) is formed (b) Observation made by the addition of dilute hydrochloric acid to 1g of powered iron (III) sulphide (FeS) 2HCl\(_{(aq)}\) + FeS\(_{(s)}\) \(\to\) FeCl\(_{(aq)}\) + H\(_2\)S\(_{(g)}\) Effervescence (bubbling) occurs or evolution of a gas with a smell of rotten eggs and a green solution is formed. (c) Observation made by the addition of 2cm\(^3\) of dillute hydrochloric acid to 1g of iron filings and allowed to stand for sometime Effervescence or evolution of colourless, odourless gas noticed with the formation of light green solution that will turn brown after sometime.

Tin is unaffected by air even at ordinary temperature because it forms a thin, protective oxide layer on it's surface. None of the options provided directly explain why tin is unaffected by air. However, for the sake of the examination and choosing the best among the four options, it will be weak electropositive character, as it implies that tin is less reactive.

Alkanones also known as ketones have the general formula RCOR'

Constituents of duralumin are: Al, Cu, Mg, Mn. Constituents of Alnico are: Al, Ni and Co In 1909, the alloy of duralumin was discovered by Alfred Wilon consisting of 94% Al, 4% Cu, 1% Mg and 1% Mn(Manganese) Alnico is an acronym referring to a family of iron alloys which in addition to iron are composed primarily of Al, Ni and Co.

The shape of the S-orbital is spherical.

Aluminium hydroxide is used in the dyeing industry as a mordant. It combines with a dye and thereby fixes it in a material.

It is also called weak iodine solution. Tincture solutions are characterized by the presence of alcohol.

Permanent hardness in water= Mg & Ca Sulphate. Temporary hardness in water= Mg & Ca Carbonate. Temporary hardness of water is caused by Magnesium and calcium hydrogencarbonate. It is formed when rainwater containing dissolved CO2 flows over deposit of CaCO3 i.e CaCO3 + CO2 + H2O → Ca(HCO3)2

H2CO3 is an example of a weak acid while H2SO4 and HNO3 are examples of a strong acid. CO2 combines with water to give a weak trioxocarbonate (IV) acid. CO2 + H2O → H2CO3