SULPHUR AND ITS COMPOUNDS FORM 3 CHEMISTRY NOTES LATEST FREE

<h1>SULPHUR AND ITS COMPOUNDS<&sol;h1>&NewLine;<p><strong> Objectives <&sol;strong><&sol;p>&NewLine;<p><strong>By the end of the Chapter&comma; the learner should be able to&colon;<&sol;strong><&sol;p>&NewLine;<p>&lpar;a&rpar;  Name the sources of sulphur&period;<&sol;p>&NewLine;<p>&lpar;b&rpar;  Describe the extraction of sulphur&period;<&sol;p>&NewLine;<p>&lpar;c&rpar;  Describe the preparation of the allotropes of sulphur&period;<&sol;p>&NewLine;<p>&lpar;d&rpar;  State the properties and uses of sulphur&period;<&sol;p>&NewLine;<p>&lpar;e&rpar;  Name and describe the preparation of the oxides of sulphur&period;<&sol;p>&NewLine;<p>&lpar;f&rpar;  State the properties and uses of the oxides of sulphur&period;<&sol;p>&NewLine;<p>&lpar;g&rpar;  Describe the contact process for the manufacture of sulphuric acid&period;<&sol;p>&NewLine;<p>&lpar;h&rpar;  Describe the properties and state the uses of sulphuric acid&period;<&sol;p>&NewLine;<p>&lpar;i&rpar;   Describe the preparation and state the properties of hydrogen sulphide&period;<&sol;p>&NewLine;<p>&lpar;j&rpar;  Explain pollution effects of sulphur containing compounds&period;<&sol;p>&NewLine;<h2><span style&equals;"text-decoration&colon; underline&semi;"><strong>SULPHUR AND ITS COMPOUNDS<&sol;strong><&sol;span><&sol;h2>&NewLine;<p>Sulphur is the second member of group VI elements&period; It is placed just below oxygen in the periodic table&period; It has an atomic number 16 hence its electron arrangement is 2&period;8&period;6&period;<&sol;p>&NewLine;<p>Sulphur occurs naturally as an element in deposits in places such as Texas and Louisiana in U&period;S&period;A&comma; Sicily in Italy&comma; and various places in Japan&period;<&sol;p>&NewLine;<p>Sulphur also occurs in combination with other elements as sulphides and sulphates&period; The sulphide ores include copper pyrites &lpar;CuFeS<sub>2<&sol;sub>&rpar; and iron pyrites &lpar;FeS<sub>2<&sol;sub>&rpar;&period;<&sol;p>&NewLine;<p>The sulphate ores include gypsum &lpar;CaSO<sub>4<&sol;sub>&period;2H<sub>2<&sol;sub>O&rpar;and anhydrite &lpar;CaSO<sub>4<&sol;sub>&rpar;&period; Petroleum gas and coal mines contain sulphur in the form of hydrogen sulphide gas&period;<&sol;p>&NewLine;<h1><a name&equals;"&lowbar;Toc51750072"><&sol;a>Sulphur and its allotropes<&sol;h1>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750073"><&sol;a>Extraction OfSulphur&colon; The Frasch process<&sol;h2>&NewLine;<p>The Frasch process is  employed in the extraction of Sulphur&period; The process is based on the low melting point of sulphur which ranges between 113 °C and 119°C&period; In the Frasch process&comma; three concentric pipes of different diameters 2 cm&comma; 8 cm&comma; and 15 cm are sunk into the sulphur deposits underground&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>Water is heated to about <strong>170°C<&sol;strong> under pressure of about<strong> 10 atmospheres<&sol;strong> and is forced down the outermost pipe&period; <strong>The pressure ensures that the water remains in liquid state at such high temperature&period;<&sol;strong><&sol;p>&NewLine;<p>Hot air at a pressure of 15 atmospheres is forced down the innermost pipe&period; <strong>This produces a light froth consisting of a mixture of molten sulphur and water&period; The high pressure forces the mixture up the middle pipe<&sol;strong>&period;<&sol;p>&NewLine;<p>The mixture is run into large tanks on the surface where the sulphur solidifies at 115°C&comma; Separates from the water and is stored&period; Sulphur obtained this way in usually over 99&percnt; pure&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750074"><&sol;a>Allotropes of Sulphur<&sol;h2>&NewLine;<p>Sulphur exhibits allotropy&period; The main allotropes are rhombic and monoclinic sulphur<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750075"><&sol;a>Rhombic Sulphur<&sol;h3>&NewLine;<p>Rhombic sulphur is also referred to as <strong>octahedral or <&sol;strong><strong>α<&sol;strong><strong>-sulphur<&sol;strong>&period; It is a bright yellow crystalline<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"23"><&sol;td>&NewLine;<td width&equals;"125"><&sol;td>&NewLine;<td width&equals;"184"><&sol;td>&NewLine;<td width&equals;"143"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td rowspan&equals;"2"><&sol;td>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>solid with an <strong>octahedral shape&period;<&sol;strong><&sol;p>&NewLine;<p><em>&lpar;a&rpar; A crystal of rhombic sulphur&period;                 <&sol;em><em>&lpar;b&rpar; Packing of rhombic sulphur molecules in a crystal<&sol;em><&sol;p>&NewLine;<p><strong>How to prepare Rhombic sulphur&colon; <&sol;strong><&sol;p>&NewLine;<p><strong>Place two spatulafuls of powdered sulphur in a boiling tube containing 10 cm<sup>3<&sol;sup> of carbon&lpar;IV&rpar; sulphide&period; Stir and filter the contents of the tube into a dry beaker using a dry filter paper&period; Allow the filtrate to evaporate slowly&period; Use a hand lens to examine the crystals formed<&sol;strong>&period;<&sol;p>&NewLine;<p>Rhombic sulphur melts at 113°C and has a density of 2&period;06 g&sol;cm<sup>3<&sol;sup>&period; It is the stable allotrope below 96°C&period; Above this temperature&comma; it slowly changes into monoclinic sulphur&period;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750076"><&sol;a>Monoclinic Sulphur<&sol;h3>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"11"><&sol;td>&NewLine;<td width&equals;"113"><&sol;td>&NewLine;<td width&equals;"208"><&sol;td>&NewLine;<td width&equals;"238"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<td rowspan&equals;"2"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>Monoclinic sulphur is also referred to as prismatic or <em>ß<&sol;em> &&num;8211&semi; sulphur&period; It is a pale yellow crystalline solid&period; The crystals appear needle-like when observed using a hand lens&period; The actual shape of the crystal is a hexagonal prism&period;<&sol;p>&NewLine;<ul>&NewLine;<li><em>A crystal of monoclinic Sulphur&period; &lpar;b&rpar; Packing of monoclinic Sulphur molecules in a crystal <&sol;em><&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong><em> <&sol;em><&sol;strong><&sol;p>&NewLine;<p><strong><em>How to prepare monoclinic sulphur<&sol;em><&sol;strong><&sol;p>&NewLine;<p>Place some powdered sulphur in an evaporating dish and heat gently until the sulphur melts&period; Using a glass rod&comma; stir and add more sulphur a little at a time until the dish is almost full of molten sulphur&period;<&sol;p>&NewLine;<p>Remove the source of heat and allow the sulphur to cool and form a crust on the surface&period; Using a thin glass rod&comma; carefully pierce two holes on widely separated points<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"316"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>in the crust as shown below &period;<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"11"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>Immediately pour out the molten sulphur&period; Remove the crust by cutting round the edge of the dish with a knife&period; Use a hand lens to observe the crystals that have formed on the underside of the crust&period;<&sol;p>&NewLine;<p>Monoclinic sulphur has a <strong>melting point of 119°C and a density of 1&period;98 g&sol;cm<sup>3<&sol;sup>&period; Below 96°C monoclinic sulphur gradually changes to rhombic sulphur&period; This temperature of 96°C is the transition temperature for rhombic and monoclinic sulphur&period; <&sol;strong><&sol;p>&NewLine;<p><strong>The temperature at which one allotrope of an element changes to another is called the transition temperature&period;<&sol;strong><&sol;p>&NewLine;<p><strong>Non-crystalline – &lpar;amorphous&rpar; forms of Sulphur <&sol;strong><&sol;p>&NewLine;<p>Include plastic&comma; colloidal&comma; and powdery sulphur&period;<&sol;p>&NewLine;<p><strong>Plastic sulphur<&sol;strong> is prepared by heating powdered sulphur until it boils&period; The boiling sulphur is then poured in a thin continuous stream into a beaker containing cold water&period; Long elastic yellow threads of plastic sulphur are formed&period;<&sol;p>&NewLine;<p>This form of sulphur is insoluble in carbon&lpar;IV&rpar; sulphide&period; It turns into hard rhombic sulphur if left for a few days&period;<&sol;p>&NewLine;<p>When dilute hydrochloric acid is added to a test-tube containing a dilute solution of sodium thiosulphate&comma; Na<sub>2<&sol;sub>S<sub>2<&sol;sub>O<sub>3<&sol;sub>&comma; a yellow precipitate of <strong>colloidal sulphur<&sol;strong> is deposited&period;<&sol;p>&NewLine;<p>N<sub>2<&sol;sub>S<sub>2<&sol;sub>O<sub>3<&sol;sub>&comma;&lpar;aq&rpar; &plus; 2HCl&lpar;aq&rpar;  2NaCl&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; S&lpar;s&rpar;<&sol;p>&NewLine;<p><strong>Powdery sulphur<&sol;strong> may be prepared by saturating distilled water with hydrogen sulphide&period; The solution is then exposed to air&period; A white powder is deposited&period;<&sol;p>&NewLine;<p>H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; Water  H<sub>2<&sol;sub>S&lpar;aq&rpar;<&sol;p>&NewLine;<p>2H<sub>2<&sol;sub>S&lpar;aq&rpar; &plus; O<sub>2<&sol;sub>&lpar;g&rpar;  2H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; 2S&lpar;s&rpar;<&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750077"><&sol;a>Physical Properties of Sulphur<&sol;h2>&NewLine;<p>Sulphur is a yellow non-metallic element&period; A molecule of sulphur consists of a puckered ring of eight atoms of sulphur joined together by strong covalent bonds as shown below&period; &period;<&sol;p>&NewLine;<p>Sulphur is soluble in organic solvents such as <strong>benzene&comma; methyl benzene&comma; and carbon&lpar;IV&rpar; sulphide&period; It does not dissolve in water&period;<&sol;strong><&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750078"><&sol;a>Effect of heat on sulphur&period;<&sol;h3>&NewLine;<p>When the yellow powder is gently heated&comma; it melts at 113°C to a clear amber liquid&period; At this temperature molten sulphur has a low viscosity&comma; and flows easily&period; This liquid is made up of rings of sulphur molecules consisting of eight atoms of sulphur&comma; S<sub>8<&sol;sub>&period;<&sol;p>&NewLine;<p>On further heating the liquid gradually darkens&period; At <strong>160°C&comma; it becomes reddish-brown&comma; and very viscous<&sol;strong> such that the test-tube may be inverted without the liquid sulphur pouring out&period; These changes are <strong>due to the breaking of the S<sub>8<&sol;sub> rings which join to form long chains with over 100&comma;000 atoms of sulphur&period; <&sol;strong>As the chains <strong>entangle with one another<&sol;strong>&comma; the viscosity of<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"21"><&sol;td>&NewLine;<td width&equals;"214"><&sol;td>&NewLine;<td width&equals;"169"><&sol;td>&NewLine;<td width&equals;"193"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<td rowspan&equals;"2"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>the liquid increases&period;<&sol;p>&NewLine;<p><em>Long chains of sulphur atoms<&sol;em>&period;<em>                                                                     Shorter chains of sulphur atoms<&sol;em><&sol;p>&NewLine;<p>Above 160°C&comma; the liquid <strong>darkens further and becomes almost black<&sol;strong>&period; Near the boiling point the liquid becomes <strong>more mobile&period; <&sol;strong>This is due to the breaking of the long chains to shorter chains&period;<&sol;p>&NewLine;<p>The liquid boils at 444°C and forms a reddish-brown vapour consisting of S<sub>8<&sol;sub>&comma; S<sub>6<&sol;sub> and S<sub>2<&sol;sub> molecules which cools to form a yellow sublimate&period; This sublimate is known as <strong>&OpenCurlyDoubleQuote;flowers of sulphur”<&sol;strong> and consists mainly of S<sub>8<&sol;sub> rings&period;<&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750079"><&sol;a>Chemical Properties of Sulphur<&sol;h2>&NewLine;<p><strong><em> <&sol;em><&sol;strong><&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750080"><&sol;a>Reaction of sulphur with oxygen&comma; iron powder and  copper<&sol;h3>&NewLine;<p>Sulphur burns in oxygen with a <strong>bright blue flame<&sol;strong> forming misty fumes with a choking smell&period;<&sol;p>&NewLine;<p>The gas is mainly sulphur&lpar;VI&rpar; oxide &lpar;sulphur dioxide&rpar; SO<sub>2<&sol;sub>&comma; with traces of sulphur&lpar;IV&rpar; oxide &lpar;sulphur trioxide&comma; SO<sub>3<&sol;sub>&rpar;&period;<&sol;p>&NewLine;<p>S&lpar;s&rpar; &plus; O<sub>2<&sol;sub>&lpar;g&rpar;  SO<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>2S&lpar;s&rpar; &plus; 3O<sub>2<&sol;sub>&lpar;g&rpar;  2SO<sub>3<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"221"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>The<strong> moist blue litmus paper turns re<&sol;strong>d indicating that the oxides produced when sulphur burns are acidic&period;<&sol;p>&NewLine;<p>Sulphur combines directly with some elements to form sulphides&period;<&sol;p>&NewLine;<ul>&NewLine;<li>When a mixture of sulphur&comma; and iron powder is heated&comma; a <strong>highly exothermic reaction occurs&period;<&sol;strong> Once the reaction has started at one point&comma; the glow spreads through the mixture without further heating&comma; forming iron&lpar;II&rpar; sulphide&period; This is because the <strong>heat produced during the reaction is high enough to sustain the reaction&period;<&sol;strong><&sol;li>&NewLine;<li>&NewLine;Hot powdered copper similarly combines with heated sulphur forming copper&lpar;I&rpar; sulphide&period;<&sol;li>&NewLine;<li>&NewLine;Sulphur also combines with some non-metals such as carbon and hydrogen forming non-metallic sulphides&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>Carbon combines with sulphur at high temperatures to form carbon&lpar;IV&rpar; sulphide&period; Hydrogen combines with sulphur to form hydrogen sulphide&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750081"><&sol;a>Reaction of sulphur with concentrated acids<&sol;h3>&NewLine;<p>Sulphur is easily oxidised by both concentrated nitric&lpar;V&rpar; and sulphuric&lpar;VI&rpar; acids&period;<&sol;p>&NewLine;<ul>&NewLine;<li>When warmed with concentrated nitric&lpar;V&rpar; acid&comma; sulphur is oxidised to sulphuric&lpar;VI&rpar; acid&period; The <strong>sulphate &lpar;<&sol;strong><strong>&rpar; ion in the acid forms a white precipitate with barium ions in the solution&period; The nitric&lpar;V&rpar; acid itself is reduced to red brown nitrogen&lpar;IV&rpar; oxide and water&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p>S&lpar;s&rpar; &plus; 6HNO<sub>3<&sol;sub>&lpar;aq&rpar;  H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; 6NO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<ul>&NewLine;<li>Concentrated sulphuric&lpar;VI&rpar; acid <strong>oxidises sulphur to sulphur&lpar;IV&rpar; oxide <&sol;strong>while the acid is <strong>reduced to sulphur&lpar;IV&rpar; oxide&comma; and water&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p>S&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>SO&comma;&lpar;l&rpar;  3SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>Concentrated hydrochloric acid does not react with sulphur because it is not an oxidising agent&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750082"><&sol;a>Uses of Sulphur<&sol;h2>&NewLine;<ul>&NewLine;<li>Manufacture of sulphuric&lpar;VI&rpar; acid&period;<&sol;li>&NewLine;<li>As a fungicide&period;<&sol;li>&NewLine;<li>In the manufacture of bleaching agent used to bleach wood pulp in the paper industry&period;<&sol;li>&NewLine;<li>Vulcanisation &lpar;hardening&rpar; of rubber&period;<&sol;li>&NewLine;<li>Used in smaller quantities in the manufacture of dyes&comma; and fireworks&period;<em>&period;<&sol;em><&sol;li>&NewLine;<&sol;ul>&NewLine;<h1><a name&equals;"&lowbar;Toc51750083"><&sol;a>The Compounds of Sulphur<&sol;h1>&NewLine;<p><strong>Sulphur forms several compounds&period; The common compounds include the oxides&comma; sulphuric acid and hydrogen sulphide<&sol;strong><&sol;p>&NewLine;<h1><a name&equals;"&lowbar;Toc51750084"><&sol;a>Oxides of Sulphur<&sol;h1>&NewLine;<p>Sulphur forms two oxides namely sulphur&lpar;IV&rpar; oxide&comma; SO<sub>2<&sol;sub>&comma; and sulphur&lpar;VI&rpar; oxide SO<sub>3<&sol;sub>&period;<&sol;p>&NewLine;<p><sub> <&sol;sub><&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750085"><&sol;a>Sulphur&lpar;IV&rpar; Oxide&comma; SO<sub>2<&sol;sub><&sol;h2>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750086"><&sol;a>Laboratory preparation of sulphur &lpar;IV&rpar; oxide&period;<&sol;h3>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide is prepared in the laboratory by the action of dilute hydrochloric acid on a suitable sulphite such as sodium sulphite&period;<&sol;p>&NewLine;<p>Na<sub>2<&sol;sub>SO<sub>3<&sol;sub>&lpar;s&rpar; &plus; 2HCl&lpar;aq&rpar;  SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2NaCl&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"113"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>The gas may also be prepared by the action of concentrated sulphuric&lpar;VI&rpar; acid on copper turnings&period; The reaction should be carried out in a fume cupboard&period;<&sol;p>&NewLine;<p>Cu&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; CuSO<sub>4<&sol;sub>&lpar;aq&rpar;<&sol;p>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide is dried by passing it through concentrated sulphuric&lpar;IV&rpar; acid and collected by downward delivery&period; The gas jar is confirmed to be full of the gas when the paper soaked in orange potassium chromate&lpar;VI&rpar; turns green&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750087"><&sol;a>Physical Properties of Sulphur&lpar;IV&rpar; Oxide<&sol;h3>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide is a colourless poisonous gas with a characteristic irritating&comma; and choking smell&period;<&sol;p>&NewLine;<p>It has a boiling point of –10°C and is readily liquefied under pressure&period;<&sol;p>&NewLine;<p><strong><em>Discussion Questions <&sol;em><&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>Give a reason why sulphur&lpar;IV&rpar; oxide is collected by downward delivery&period; <&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>It is denser than air&comma; hence can be collected by downward delivery&period;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li><strong>Explain the observation made when a test-tube full of sulphur&lpar;IV&rpar; oxide is inverted in a trough of water&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>When a test-tube full of the gas is inverted in a trough of water&comma; the water level rises rapidly inside the test-tube&period; This shows that the gas is soluble in water&period;<&sol;p>&NewLine;<ol start&equals;"3">&NewLine;<li><strong>Explain the observation made when&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;a&rpar;  A damp litmus paper was dropped into a test-tube containing sulphur&lpar;IV&rpar; oxide gas&period;<&sol;strong><&sol;p>&NewLine;<p>When a moist blue litmus paper is dropped into a test-tube containing sulphur&lpar;IV&rpar; oxide&comma; it turns red showing that the gas is acidic&period; The gas has no effect on dry litmus&period; The solution of the gas in water is sulphuric&lpar;IV&rpar; acid&period; This is a weak dibasic acid&period;<&sol;p>&NewLine;<p>SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;  H<sub>2<&sol;sub>SO<sub>3<&sol;sub>&lpar;aq&rpar;<&sol;p>&NewLine;<p>The acid is responsible for the change in colour of the moist litmus&period;<&sol;p>&NewLine;<ul>&NewLine;<li><strong>Sodium hydroxide solution is added to sulphur&lpar;IV&rpar; oxide&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p>When sodium hydroxide solution is added to sulphur&lpar;IV&rpar; oxide gas&comma; neutralisation occurs&period; The sulphuric&lpar;IV&rpar; acid formed reacts with sodium hydroxide forming a salt and water&period; During the reaction between the acid and sodium hydroxide&comma; two types of salts are formed&comma; a normal and an acid salt&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750088"><&sol;a>Chemical Properties of Sulphur &lpar;IV&rpar; Oxide<&sol;h3>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750089"><&sol;a>Bleaching Action of Sulphur&lpar;IV&rpar; Oxide<&sol;h4>&NewLine;<p>Sulphur&lpar;IV&rpar; Oxide is a bleaching agent&period; It bleaches by reduction&period; This property is applied in paper industries to bleach paper&period;<&sol;p>&NewLine;<p><strong>Discussion Questions <&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>State and explain what is observed when coloured flowers are dropped in a gas jar containing Sulphur &lpar;IV&rpar; oxide&period; <&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>When coloured flowers are dropped into a gas jar containing sulphur&lpar;VI&rpar; oxide&comma; the flowers are bleached&period; Sulphur&lpar;IV&rpar; oxide combines first with the moisture&comma; forming sulphuric&lpar;IV&rpar; acid&period; The sulphuric&lpar;IV&rpar; acid then combines with oxygen from the dye to form sulphuric&lpar;VI&rpar; acid&period; When the dye loses oxygen it becomes colourless&period; In this reaction&comma; the dye undergoes reduction while the sulphuric&lpar;IV&rpar; acid is oxidised&period;<&sol;p>&NewLine;<p>SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;  H<sub>2<&sol;sub>SO<sub>3<&sol;sub>&lpar;aq&rpar;<&sol;p>&NewLine;<p>H<sub>2<&sol;sub>SO<sub>3<&sol;sub>&lpar;aq&rpar; &plus; Dye  H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; Colourless material&period;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li><strong>Give a reason why newsprint paper turns brown after some time&period; <&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>During the manufacture of paper&comma; reducing agents such as sulphuric&lpar;IV&rpar; acid are used to bleach the materials&period; When such paper is exposed to the atmosphere in the presence of sunlight&comma; the oxygen removed during bleaching is restored&period; This explains why newsprint paper turns brown after sometime&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750090"><&sol;a>Reducing Action of Sulphur&lpar;IV&rpar; Oxide<&sol;h4>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide is a strong reducing agent&period; The reducing property is only displayed when the gas is in aqueous state&period;<&sol;p>&NewLine;<p><strong><em>Discussion Questions<&sol;em><&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>Explain the observations made when sulphur&lpar;IV&rpar; oxide gas is reacted with&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;i&rpar;  Acidified potassium chromate&lpar;VI&rpar; solution&period;<&sol;strong><&sol;p>&NewLine;<p>Acidified potassium dichromate&lpar;VI&rpar; turns from orange to green when reacted with sulphur&lpar;IV&rpar; oxide&period; The chromium&lpar;VI&rpar; ion in the dichromate &lpar;&rpar; is reduced to chromium&lpar;III&rpar; ion&period;<&sol;p>&NewLine;<p><strong>This is a test for Sulphur &lpar;IV&rpar; Oxide <&sol;strong><&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<p><strong>&lpar;ii&rpar;  Acidified potassium manganate&lpar;VII&rpar; solution<&sol;strong><&sol;p>&NewLine;<p>The colour of acidified potassium manganate&lpar;VII&rpar; turns from purple to colourless when reacted with sulphur&lpar;IV&rpar; oxide&period; This is because the manganese&lpar;VII&rpar; ion in the manganate ion &lpar;&rpar; is reduced to manganese&lpar;II&rpar; ion&period;<&sol;p>&NewLine;<p><strong>&lpar;iii&rpar; Acidified bromine water followed by a few drops of barium chloride solution&period;<&sol;strong><&sol;p>&NewLine;<p>Red brown acidified bromine water is decolourised when reacted with sulphur&lpar;IV&rpar; oxide&period; The bromine water is reduced to hydrobromic acid as the sulphur&lpar;IV&rpar; oxide is oxidised to sulphate&period;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li><strong>Explain the observations made when&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;i&rpar;   Concentrated nitric&lpar;V&rpar; acid is added to a test-tube full of sulphur&lpar;IV&rpar; oxide&comma; followed by barium chloride solution&period;<&sol;strong><&sol;p>&NewLine;<p>When concentrated nitric&lpar;V&rpar; acid is added to a test-tube containing sulphur&lpar;IV&rpar; oxide gas brown fumes of nitrogen&lpar;IV&rpar; oxide are given off&period;<&sol;p>&NewLine;<p>The nitric&lpar;V&rpar; acid is reduced to nitrogen&lpar;IV&rpar; oxide while the sulphuric&lpar;IV&rpar; acid is oxidised to sulphuric&lpar;VI&rpar; acid&period; When a solution of barium chloride is added to the mixture&comma; a white precipitate of barium sulphate is formed indicating the presence of sulphate&comma;  ions&period;<&sol;p>&NewLine;<p><strong>&lpar;ii&rpar;  Sulphur&lpar;IV&rpar; oxide is reacted with a hot solution of iron&lpar;II&rpar; chloride&period;<&sol;strong><&sol;p>&NewLine;<p>When warm iron&lpar;III&rpar; chloride solution is added to sulphur&lpar;IV&rpar; oxide the yellow colour changes to green&period; Sulphur&lpar;IV&rpar; oxide reduces yellow iron&lpar;III&rpar; ions&comma; Fe<sup>3&plus;<&sol;sup>&lpar;aq&rpar; to pale green iron&lpar;II&rpar;&comma; Fe<sup>2&plus;<&sol;sup>&lpar;aq&rpar; ions&period;<&sol;p>&NewLine;<p><strong>&lpar;iii&rpar; Sulphur &lpar;IV&rpar; Oxide is reacted with hydrogen peroxide <&sol;strong><&sol;p>&NewLine;<p>Similarly&comma; hydrogen peroxide is reduced to water&period;<&sol;p>&NewLine;<p><strong>&lpar;Iv&rpar; A burning splint is lowered into a gas jar containing Sulphur &lpar;IV&rpar; oxide&period; <&sol;strong><&sol;p>&NewLine;<p>When a burning splint is lowered into a test-tube containing sulphur&lpar;IV&rpar; oxide&comma; it is put off showing that the gas does not support combustion or burn&period; However&comma; in the presence of a catalyst&comma; the gas is oxidised to sulphur&lpar;VI&rpar; oxide&period;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750091"><&sol;a>Oxidising Action of Sulphur&lpar;IV&rpar; Oxide<&sol;h4>&NewLine;<p>Sulphur &lpar;IV&rpar; Oxide also acts as an Oxidising agent&period; It oxidises burning magnesium to magnesium oxide and hydrogen sulphide to Sulphur&period;<&sol;p>&NewLine;<p><strong>Discussion <em>Questions<&sol;em><&sol;strong><&sol;p>&NewLine;<p><strong>Explain the observations made when burning magnesium is lowered into a gas jar of sulphur&lpar;IV&rpar; oxide&period;<&sol;strong><&sol;p>&NewLine;<p>When burning magnesium is lowered into a gas jar of sulphur&lpar;IV&rpar; oxide&comma; it continues to burn for some time&period; White fumes of magnesium oxide&comma; and yellow specks of sulphur are formed&period;<&sol;p>&NewLine;<p>Burning magnesium continues to burn in sulphur&lpar;IV&rpar; oxide because the heat produced by the burning magnesium decomposes the sulphur&lpar;IV&rpar; oxide to sulphur and oxygen&period; The magnesium combines with the oxygen to form magnesium oxide&period;<&sol;p>&NewLine;<p>In this reaction&comma; sulphur&lpar;IV&rpar; oxide is an oxidising agent&comma; supplying oxygen to magnesium&period;<&sol;p>&NewLine;<p><strong>Explain the observations made when a gas jar of dry hydrogen sulphide gas is inverted over a test-tube containing Sulphur&lpar;IV&rpar; Oxide and a few drops of water added&period; <&sol;strong><&sol;p>&NewLine;<p>When a gas jar of dry hydrogen sulphide gas is inverted over a test-tube containing dry sulphur&lpar;IV&rpar; oxide&comma; there is no observable change&period; When a few drops of water are added into each gas jar and the mixture is shaken&comma; a yellow deposit of sulphur is produced&period;<&sol;p>&NewLine;<p>2H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar;  3S&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>The reaction only takes place when the gases are moist&period; Sulphur&lpar;IV&rpar; oxide acts as an oxidising agent&period;<&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750092"><&sol;a>Sulphur &lpar;VI&rpar; Oxide&comma; SO<sub>3<&sol;sub><&sol;h2>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750093"><&sol;a>Preparation of Sulphur &lpar;VI&rpar; Oxide &lpar;SO<sub>3<&sol;sub>&rpar;<&sol;h3>&NewLine;<p>In the laboratory&comma; sulphur&lpar;VI&rpar; oxide is prepared by reacting sulphur&lpar;IV&rpar; oxide with oxygen in the presence of a platinum catalyst&period;&period;<&sol;p>&NewLine;<p><em>Lab Preparation of Sulphur Trioxide&comma; SO<sub>3<&sol;sub><&sol;em><&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>Equation for the reaction taking place&comma;<&sol;p>&NewLine;<p>2SO<sub>2<&sol;sub>&lpar;g&rpar;&plus; O<sub>2<&sol;sub>&lpar;g&rpar;  2SO<sub>3<&sol;sub>&lpar;s&rpar;<&sol;p>&NewLine;<p>Other Methods<&sol;p>&NewLine;<p>Decomposing of sodium hydrogen sulphate&period;<&sol;p>&NewLine;<p><strong><em>Discussion Questions<&sol;em><&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>State the purpose of the following in the set up&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;a&rpar;  Concentrated sulphuric&lpar;VI&rpar; acid&period;<&sol;strong><&sol;p>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide and oxygen gases are dried by passing them through concentrated sulphuric&lpar;VI&rpar; acid<&sol;p>&NewLine;<p><strong>&lpar;b&rpar;  Freezing salt ice mixture<&sol;strong>&period;<&sol;p>&NewLine;<p>The sulphur&lpar;VI&rpar; oxide is cooled by the freezing salt-ice mixture and it solidifies&period;<&sol;p>&NewLine;<p><strong>&lpar;c&rpar;  Anhydrous calcium chloride&period;<&sol;strong><&sol;p>&NewLine;<p>Since sulphur&lpar;VI&rpar; oxide is deliquescent&comma; calcium chloride is used to keep it free from moisture<&sol;p>&NewLine;<ol>&NewLine;<li><strong>Write an equation for the reaction that takes place in the combustion tube&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>2SO<sub>2<&sol;sub>&lpar;g&rpar;&plus; O<sub>2<&sol;sub>&lpar;g&rpar;  2SO<sub>3<&sol;sub>&lpar;s&rpar;<&sol;p>&NewLine;<ol>&NewLine;<li><strong>Comment on the method of collection of sulphur&lpar;VI&rpar; oxide&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>The sulphur&lpar;VI&rpar; oxide is cooled by the freezing salt-ice mixture and it solidifes&period; This allows it to be collected as illustrated&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750094"><&sol;a>Test for Sulphate and Sulphite ions&period;<&sol;h2>&NewLine;<p>The addition of bariumchloride on sodium sulphate and sodium sulphite is used to test for sulphate and sulphite ions&period;<&sol;p>&NewLine;<p><strong>Test<&sol;strong><&sol;p>&NewLine;<p><strong>To 2 cm<sup>3<&sol;sup> of sodium sulphate in a test-tube&colon;<&sol;strong><&sol;p>&NewLine;<p>&lpar;i&rpar;  Add 2 cm<sup>3<&sol;sup> of barium chloride&lpar;or nitrate&rpar; solution&period;<&sol;p>&NewLine;<p>&lpar;ii&rpar;  To the mixture in&lpar;i&rpar; above add 2 cm<sup>3<&sol;sup> of dilute hydrochloric acid &lpar;or dilute nitric&lpar;V&rpar; acid&rpar;&period;<&sol;p>&NewLine;<p>Repeat procedure &lpar;i&rpar; and &lpar;ii&rpar; using 2 cm<sup>3<&sol;sup> solution of sodium sulphite&period;<&sol;p>&NewLine;<p><strong><em>Discussion Questions <&sol;em><&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>State the observations made when barium chloride solution is added to&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;a&rpar;  Sodium sulphate solution and barium sulphite solutions&period; <&sol;strong><&sol;p>&NewLine;<p>When barium chloride solution is added to sodium sulphate and sodium sulphite solutions&comma; a white precipitate is formed in each case&period; The white precipitates are barium sulphate and barium sulphite respectively&period;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li><strong>Why is the acid added to the mixture&quest;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>The acid is  added to <strong>distinguish between the sulphate and sulphite ions&period; <&sol;strong><&sol;p>&NewLine;<p>When dilute hydrochloric acid is added to the mixture containing barium sulphate precipitate&comma; the precipitate does not dissolve&period;<&sol;p>&NewLine;<p><strong>However&comma; when dilute hydrochloric acid is added to the mixture containing barium sulphite precipitate&comma; the precipitate dissolves&period; This is the test for sulphite ions&period;<&sol;strong><&sol;p>&NewLine;<p>BaSO<sub>3<&sol;sub>&lpar;s&rpar; &plus; 2HCl&lpar;aq&rpar;  BaCl<sub>2<&sol;sub>&lpar;aq&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>BaSO<sub>3<&sol;sub>&lpar;s&rpar; &plus; 2H<sup>&plus;<&sol;sup>&lpar;aq&rpar;  Ba<sup>2&plus;<&sol;sup>&lpar;aq&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750095"><&sol;a>Uses of Sulphur&lpar;VI&rpar; Oxide<&sol;h3>&NewLine;<p>Sulphur&lpar;VI&rpar; oxide is used&colon;<&sol;p>&NewLine;<ul>&NewLine;<li>As a major raw material in the large scale manufacture of sulphuric&lpar;VI&rpar; acid&period;<&sol;li>&NewLine;<li>To make calcium hydrogen sulphite&comma; Ca&lpar;HSO<sub>3<&sol;sub>&rpar;<sub>2&comma;<&sol;sub> used to bleach wood pulp in the manufacture of paper&period;<&sol;li>&NewLine;<li>As a fumigant&period;<&sol;li>&NewLine;<li>As a preservative in jam and fruit juices&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h1><a name&equals;"&lowbar;Toc51750096"><&sol;a>Sulphuric &lpar;VI&rpar; acid<&sol;h1>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750097"><&sol;a>Large Scale Manufacture of Sulphuric&lpar;VI&rpar; Acid<&sol;h2>&NewLine;<p>Sulphuric&lpar;IV&rpar; acid is manufactured by the <strong>contact process shown <&sol;strong><strong>below&period; <&sol;strong><&sol;p>&NewLine;<table>&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"33"><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td><&sol;td>&NewLine;<td><&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>The raw materials for its manufacture are <strong>sulphur&lpar;IV&rpar; oxide and air&period; <&sol;strong><&sol;p>&NewLine;<p>Sulphides or sulphur are burnt in air to produce sulphur&lpar;IV&rpar; oxide&period;<&sol;p>&NewLine;<ul>&NewLine;<li><strong>Burning of sulphur is the most convenient method of producing sulphur&lpar;IV&rpar; oxide&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong>S&lpar;s&rpar; &plus; O<sub>2<&sol;sub>&lpar;g&rpar; <&sol;strong><strong> SO<sub>2<&sol;sub>&lpar;g&rpar;<&sol;strong><&sol;p>&NewLine;<p>The sulphur&lpar;IV&rpar; oxide contains<strong> dust particles<&sol;strong> as <strong>impurities&period; <&sol;strong><&sol;p>&NewLine;<ul>&NewLine;<li><strong>The impurities reduce the surface area of the catalyst&comma; thus impairing its efficiency&period;<&sol;strong> These impurities are said to <strong>poison the catalyst&period;<&sol;strong><&sol;li>&NewLine;<li>The dust impurities are removed by <strong>electrostatic precipitation<&sol;strong>&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>The mixture of gases is passed through<strong> concentrated sulphuric&lpar;VI&rpar; acid in order to dry it&period;<&sol;strong><&sol;p>&NewLine;<p>After purification&comma; the gaseous mixture is <strong>pre-heated<&sol;strong> in the heat exchanger to <strong>attain suitable reaction temperature<&sol;strong> before being passed into the catalytic chamber&period;<&sol;p>&NewLine;<p>In the catalytic chamber&comma; sulphur&lpar;IV&rpar; oxide and oxygen react to form sulphur&lpar;VI&rpar; oxide&period;<&sol;p>&NewLine;<p>Either <strong>platinum or vanadium&lpar;V&rpar; oxide<&sol;strong> may be used as catalyst&period;<&sol;p>&NewLine;<ul>&NewLine;<li>However&comma; the <strong>vanadium&lpar;V&rpar; oxide&lpar;V<sub>2<&sol;sub>O<sub>5<&sol;sub>&rpar; is preferred because it is cheaper and less easilypoisoned&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p>For maximum yield of sulphur&lpar;VI&rpar; oxide in the contact process&comma; <strong>low temperature and high pressure<&sol;strong> are necessary&period;<&sol;p>&NewLine;<ul>&NewLine;<li>However&comma; at<strong> low temperature the reaction is slow <&sol;strong>while <strong>high pressure is expensive tomaintain<&sol;strong>&period; A <strong>temperature of 450°C and pressure of 2 to 3 atmospheres <&sol;strong>are used and are referred to as <strong>optimum conditions<&sol;strong>&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong>The sulphur&lpar;VI&rpar; oxide is not dissolved directly in water because the excessive heat generated could boil the acid to produce a mist of fine droplets of sulphuric&lpar;VI&rpar; acid in air&period; Hence&comma; the gas is dissolved in concentrated sulphuric&lpar;VI&rpar; acid to form oleum &lpar;H<sub>2<&sol;sub>S<sub>2<&sol;sub>O<sub>7<&sol;sub>&rpar;&period;<&sol;strong><&sol;p>&NewLine;<ul>&NewLine;<li>&NewLine;Sulphuric&lpar;VI&rpar; acid is obtained by <strong>diluting oleum with water&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong>H<sub>2<&sol;sub>S<sub>2<&sol;sub>O<sub>7<&sol;sub>&lpar;1&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; <&sol;strong><strong> 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;<&sol;strong><&sol;p>&NewLine;<p>During the contact process&comma; not all the sulphur&lpar;IV&rpar; oxide is converted into sulphur &lpar;VI&rpar; oxide&colon;<strong> only 98&percnt; conversion of sulphur&lpar;IV&rpar; oxide to sulphur&lpar;VI&rpar; oxide occurs&period;<&sol;strong><&sol;p>&NewLine;<ul>&NewLine;<li>Sulphur&lpar;IV&rpar; oxide is a <strong>pollutant<&sol;strong>&comma; passing the exhaust gases through chimneys lined with calcium hydroxide reduces the amount of sulphur&lpar;IV&rpar; oxide released to the atmosphere&period; This is referred to as <strong>scrubbing the gas&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong>Ca&lpar;OH&rpar;<sub>2<&sol;sub>&lpar;aq&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; <&sol;strong><strong> CaSO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;strong><&sol;p>&NewLine;<ul>&NewLine;<li>In some industries&comma; filters fitted with strong alkalis are installed to remove any traces of acid or mist from exhaust gases&period;<&sol;li>&NewLine;<li><&sol;li>&NewLine;<&sol;ul>&NewLine;<h2><a name&equals;"&lowbar;Toc51750098"><&sol;a>Properties of Sulphuric&lpar;VI&rpar; acid<&sol;h2>&NewLine;<p>Concentrated sulphuric&lpar;VI&rpar; acid is a colourless oily liquid&period;<&sol;p>&NewLine;<p>It has a density of 1&period;84 g&sol;cm<sup>3<&sol;sup> and boils at 338°C&period;<&sol;p>&NewLine;<p>It is very soluble in water&period; It dissolves with evolution of heat &lpar;exothermic reaction&rpar;<&sol;p>&NewLine;<p><strong>Concentrated sulphuric&lpar;VI&rpar; acid is hygroscopic<&sol;strong>&period; This property makes the acid a suitable <strong>drying agent<&sol;strong> for gases which do not react with it&period; The acid readily removes water from hydrated salts&period;<&sol;p>&NewLine;<p>Concentrated sulphuric&lpar;VI&rpar; acid is a <strong>strong dehydrating agent&period; <&sol;strong><&sol;p>&NewLine;<p>A <strong>dehydrating agent<&sol;strong><em>is a substance which is capable of removing chemically combined water or the elements of water from a compound<&sol;em>&period;<&sol;p>&NewLine;<p>The process of removing water or its elements from a compound is called <strong>dehydration&period; <&sol;strong><&sol;p>&NewLine;<p>The acid dehydrates alcohols to to alkenes&comma; methanoic acid to carbon&lpar;II&rpar; oxide and sugar to carbon&period; The sugar crystals are charred to a black mass when concentrated sulphuric &lpar;VI&rpar; acid is added to it&period;<&sol;p>&NewLine;<p>Hot concentrated sulphuric&lpar;VI&rpar; acid is a strong <strong>oxidising agent&period;<&sol;strong>It oxidises metals such as copper and non metals such as carbon and sulphur&period;<&sol;p>&NewLine;<p>It is also a<strong> less volatile acid and displaces more volatile acids <&sol;strong>from their salts&period;<&sol;p>&NewLine;<p><strong><em>Discussion Questions<&sol;em><&sol;strong><&sol;p>&NewLine;<ol>&NewLine;<li><strong>Explain why the acid should be added to water and not water to acid&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>If water is added to the acid&comma; <strong>fumes<&sol;strong> are produced since the reaction is quite <strong>exothermic<&sol;strong>&period; For this reason&comma; dilution of the concentrated acid should always be carried out by adding small portions of the acid slowly to a large volume of water with constant stirring&period;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li><strong>Explain the observation made when concentrated sulphuric&lpar;VI&rpar; acid was added to&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;a&rpar;  Copper&lpar;II&rpar; sulphate crystals&period;<&sol;strong><&sol;p>&NewLine;<p>When the acid is added to blue crystals of copper&lpar;II&rpar; sulphate pentahydrate&comma; CuSO<sub>4<&sol;sub>&period;5H<sub>2<&sol;sub>O&comma; a white powder of the anhydrous salt is formed&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li><strong>Sugar crystals&period;<&sol;strong><&sol;li>&NewLine;<&sol;ul>&NewLine;<p>When concentrated sulphuric&lpar;VI&rpar; acid is added to sugar crystals&comma; the crystals are charred to a black mass&period;<&sol;p>&NewLine;<p><strong>&lpar;c&rpar; Methanoic acid and ethanol <&sol;strong><&sol;p>&NewLine;<p>Methanoic acid is dehydrated to form carbon&lpar;II&rpar; oxide&period;<&sol;p>&NewLine;<p>The acid also dehydrates alcohols to alkenes&period;<&sol;p>&NewLine;<ul>&NewLine;<li><&sol;li>&NewLine;<&sol;ul>&NewLine;<ol start&equals;"3">&NewLine;<li><strong>Explain the observations made when concentrated sulphuric&lpar;IV&rpar; acid was reacted with&colon;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p><strong>&lpar;a&rpar;  Copper and zinc metals<&sol;strong><&sol;p>&NewLine;<p>When copper or zinc metal is added to concentrated sulphuric&lpar;IV&rpar; acid&comma; a gas is produced which turns acidified potassium chromate&lpar;VI&rpar; solution from orange to green and decolourises acidified potassium manganate&lpar;VII&rpar; solution&period;<&sol;p>&NewLine;<p>Cu&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  CuSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>Zn&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  ZnSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p><strong>&lpar;b&rpar;  Carbon and Sulphur powder&period;<&sol;strong><&sol;p>&NewLine;<p>Hot concentrated sulphuric&lpar;VI&rpar; acid  <strong>oxidises<&sol;strong> non-metals such as <strong>sulphur<&sol;strong> and <strong>carbon<&sol;strong>&period;<&sol;p>&NewLine;<p>S&lpar;s&rpar; &plus; 2H<sub>4<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  3SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>C&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  2SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; CO<sub>2<&sol;sub> &lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<ol start&equals;"4">&NewLine;<li><strong>Explain the observation made when concentrated sulphuric&lpar;VI&rpar; acid was added toPotassium nitrate crystals and Sodium chloride&period;<&sol;strong><&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Concentrated sulphuric&lpar;IV&rpar; acid is<strong> a less volatile acid&period;<&sol;strong> It displaces more volatile acids from their salts&period;<&sol;p>&NewLine;<p>KNO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  HNO<sub>3<&sol;sub>&lpar;g&rpar; &plus; KHSO<sub>4<&sol;sub>&lpar;s&rpar;<&sol;p>&NewLine;<p>NaCl&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar;  HCl&lpar;s&rpar; &plus; NaHSO<sub>4<&sol;sub>&lpar;s&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750099"><&sol;a>Reactions of Dilute Sulphuric&lpar;VI&rpar; Acid<&sol;h2>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750100"><&sol;a>Reactions with metals<&sol;h3>&NewLine;<p>When dilute sulphuric&lpar;VI&rpar; acid is added to magnesium or zinc&comma; an <strong>effervescence occurs as a colourless gas which produces a &OpenCurlyQuote;pop’ sound when a burning splint is applied is produced&period;<&sol;strong> The reaction between magnesium and dilute sulphuric acid is more vigorous than that of zinc and dilute sulphuric&lpar;VI&rpar; acid&period;<&sol;p>&NewLine;<p>Mg&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub> &lpar;aq&rpar;  MgSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>Zn&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  ZnSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>Copper is below hydrogen in the reactivity series of the metals&period; It does not therefore displace hydrogen from dilute sulphuric&lpar;VI&rpar; acid&period;<&sol;p>&NewLine;<p>The reactions between metals high in the reactivity series such as potassium and sodium with dilute acids are very <strong>violent<&sol;strong> and<strong> should never be attempted<&sol;strong>&period; The vigour of the reaction <strong>decreases<&sol;strong> as you go <strong>down the reactivity series&period;<&sol;strong><&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750101"><&sol;a>Reactions with carbonates&period;<&sol;h3>&NewLine;<p>Effervescence occurs when dilute sulphuric&lpar;VI&rpar; acid is added to <strong>the carbonates of zinc&comma; sodium and copper&period;<&sol;strong> The colourless gas produced forms a<strong> white precipitate with lime water showing that it is carbon&lpar;IV&rpar; oxide&period;<&sol;strong><&sol;p>&NewLine;<p>ZnCO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  ZnSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; CO<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>Na<sub>2<&sol;sub>CO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  Na<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; CO<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>CuCO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  CuSO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; CO<sub>2<&sol;sub>&lpar;s&rpar;<&sol;p>&NewLine;<p>The reaction between <strong>calcium carbonate and dilute sulphuric &lpar;VI&rpar; acid stops soon after it starts&period; This is because the calcium sulphate produced during the reaction is insoluble&period;<&sol;strong><&sol;p>&NewLine;<p>CaCO<sub>3<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  CaSO<sub>4<&sol;sub>&lpar;s&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; CO<sub>2<&sol;sub>&lpar;g&rpar;<&sol;p>&NewLine;<p>The insoluble calcium sulphate forms a <strong>coating<&sol;strong> on the <strong>sulphate calcium preventing further contact with the acid&period; As a result the reaction stops&period; Lead&lpar;II&rpar; carbonate behaves in a similar manner&period;<&sol;strong><&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750102"><&sol;a>Reaction with metal oxides and hydroxides<&sol;h3>&NewLine;<p>When dilute sulphuric&lpar;VI&rpar; acid reacts with a metal oxide or hydroxide&comma; a<strong> salt and water<&sol;strong> are formed&period; However&comma; those metal oxides whose sulphates are <strong>insoluble<&sol;strong> react only for a short while&period;<&sol;p>&NewLine;<p>Thus&comma; the reaction between dilute sulphuric&lpar;VI&rpar; acid&comma; and lead&lpar;II&rpar; oxide stops almost immediately&period; This is due to the formation of an insoluble layer of lead&lpar;II&rpar; sulphate which effectively prevents further contact between the acid and the oxide&period;<&sol;p>&NewLine;<p>2NaOH&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar;  Na<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750103"><&sol;a>Uses of Sulphuric&lpar;VI&rpar; acid<&sol;h2>&NewLine;<ol>&NewLine;<li>Manufacture of fertilisers&period;<&sol;li>&NewLine;<li>Processing of metal ores&period;<&sol;li>&NewLine;<li>Manufacture of detergents&period;<&sol;li>&NewLine;<li>Manufacture of plastics&period;<&sol;li>&NewLine;<li>Manufacture of dyes and paints&period;<&sol;li>&NewLine;<li>Used in lead acid accumulators<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h1><a name&equals;"&lowbar;Toc51750104"><&sol;a>Hydrogen Sulphide &lpar;H<sub>2<&sol;sub>S&rpar;<&sol;h1>&NewLine;<p>Hydrogen sulphide is a gaseous compound of sulphur which is very poisonous&period; It occurs naturally in some deposits mixed with natural gas&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h2><a name&equals;"&lowbar;Toc51750105"><&sol;a>Preparation and properties of hydrogen sulphide<&sol;h2>&NewLine;<p>The set-up below can be used to prepare hydrogen sulphide&period;<&sol;p>&NewLine;<p><em>&period;<&sol;em><&sol;p>&NewLine;<p>Hydrogen sulphide is formed when dilute hydrochloric acid is added to iron&lpar;II&rpar; sulphide&period;<&sol;p>&NewLine;<p>FeS&lpar;s&rpar; &plus; 2HCl&lpar;aq&rpar;  FeCl<sub>2<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;g&rpar;<&sol;p>&NewLine;<p>However&comma; any metal sulphide&comma; and dilute acid can be used to prepare hydrogen sulphide gas&period;<&sol;p>&NewLine;<p>The gas is collected over warm water since it dissolves in cold water&period;<&sol;p>&NewLine;<p>The gas can be dried by passing it through a U-tube packed with<strong>anyhydrous calcium chloride&period; <&sol;strong><&sol;p>&NewLine;<p><strong>The gas cannot be dried using concentrated sulphuric&lpar;VI&rpar; acid because it would be oxidised to sulphur&period;<&sol;strong><&sol;p>&NewLine;<p><strong>3H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;l&rpar; <&sol;strong><strong> 4S&lpar;s&rpar; &plus; 4H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;strong><&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750106"><&sol;a>Physical properties of hydrogen sulphide<&sol;h3>&NewLine;<p>Hydrogen sulphide is a colourless gas with a characteristic smell of rotten eggs&period; It is very poisonous&period; It is slightly soluble in cold water&period; It is denser than air&period;<&sol;p>&NewLine;<h3><a name&equals;"&lowbar;Toc51750107"><&sol;a>Chemical properties of hydrogen sulphide<&sol;h3>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750108"><&sol;a>&lpar;a&rpar; Reaction with water<&sol;h4>&NewLine;<p>Hydrogen sulphide dissolves in water to form a weak acidic solution of H<sub>2<&sol;sub>S&lpar;aq&rpar;&period;<&sol;p>&NewLine;<p>Aqueous hydrogen sulphide is a weak dibasic acid&period; It forms two types of salts&comma; the hydrogen sulphides&comma; and the sulphides&comma; e&period;g&period;&comma; sodium hydrogen sulphide &lpar;NaHS&rpar; and sodium sulphide &lpar;Na<sub>2<&sol;sub>S&rpar;&period;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750109"><&sol;a>&lpar;b&rpar; Reaction with Oxygen<&sol;h4>&NewLine;<p>Hydrogen sulphide burns in air with a pale blue flame&period; In a limited supply of air&comma; sulphur and water are formed&period;<&sol;p>&NewLine;<p>2H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; O<sub>2<&sol;sub>&lpar;g&rpar;  2S&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;g&rpar;<&sol;p>&NewLine;<p>In excess air&comma; sulphur&lpar;IV&rpar; oxide and water are formed&period;<&sol;p>&NewLine;<p>2H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; 3O<sub>2<&sol;sub>&lpar;g&rpar;  2SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;g&rpar;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750110"><&sol;a>&lpar;c&rpar; Reactions of hydrogen sulphide as a reducing agent<&sol;h4>&NewLine;<p>Hydrogen sulphide is a strong reducing agent and is readily oxidised to sulphur&comma; which is precipitated as a yellow solid&period; Red-brown bromine water is reduced by hydrogen sulphide forming colourless hydrogen bromide solution and a yellow precipitate of sulphur&period;<&sol;p>&NewLine;<p>Br<sub>2<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;g&rpar;  2HBr&lpar;aq&rpar; &plus; S&lpar;s&rpar;<&sol;p>&NewLine;<p>Yellow iron&lpar;III&rpar; chloride in solution is reduced to green iron&lpar;II&rpar; chloride&period;<&sol;p>&NewLine;<p>H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; 2FeCl<sub>3<&sol;sub>&lpar;aq&rpar;  2FeCl<sub>2<&sol;sub>&lpar;aq&rpar; &plus; S&lpar;s&rpar; &plus; 2HCl&lpar;aq&rpar;<&sol;p>&NewLine;<p>Acidified purple potassium manganate&lpar;VII&rpar; solution is reduced to a colourless manganese&lpar;II&rpar; solution&period;<&sol;p>&NewLine;<p>Similarly&comma; acidified orange chromate&lpar;VI&rpar; is reduced to green chromium&lpar;III&rpar; ions solution&period;<&sol;p>&NewLine;<p>A solution of hydrogen peroxide is reduced to water&comma; and a yellow precipitate of sulphur is formed&period;<&sol;p>&NewLine;<p>H<sub>2<&sol;sub>O<sub>2<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;g&rpar;  2H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; S&lpar;s&rpar;<&sol;p>&NewLine;<p>Brown fumes of nitrogen&lpar;IV&rpar; oxide are produced and pale yellow sulphur is deposited when hydrogen sulphide is bubbled into dilute nitric&lpar;V&rpar; acid&period;<&sol;p>&NewLine;<p>2HNO<sub>3<&sol;sub>&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;g&rpar;  2NO<sub>2<&sol;sub>&lpar;g&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar; &plus; S&lpar;s&rpar;<&sol;p>&NewLine;<p>Dilute sulpharic&lpar;VI&rpar; acid is reduced to sulphur by hydrogen sulphide&period;<&sol;p>&NewLine;<p>H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; 3H<sub>2<&sol;sub>S&lpar;g&rpar;  4S&lpar;s&rpar; &plus; 4H<sub>2<&sol;sub>O&lpar;T&rpar;<&sol;p>&NewLine;<h4><a name&equals;"&lowbar;Toc51750111"><&sol;a>&lpar;d&rpar; Reaction with aqueous metallic ious<&sol;h4>&NewLine;<p>Hydrogen sulphide reacts with some metal ions in solution to form precipitates of metal sulphides&period; When bubbled through aqueous copper&lpar;II&rpar; sulphate&comma; a black precipitate of copper&lpar;II&rpar; sulphide is formed&period;<&sol;p>&NewLine;<p>Cu<sup>2&plus;<&sol;sup>&lpar;aq&rpar; &plus; S<sup>2-<&sol;sup>&lpar;aq&rpar; CuS&lpar;s&rpar;<&sol;p>&NewLine;<p>Other metal sulphides are precipitated as shown by the following ionic equations&period;<&sol;p>&NewLine;<p>Zn<sup>2&plus;<&sol;sup>&lpar;aq&rpar; &plus; S<sup>2-<&sol;sup>&lpar;aq&rpar;  ZnS&lpar;s&rpar;<&sol;p>&NewLine;<p>Pb<sup>2&plus;<&sol;sup>&lpar;aq&rpar; &plus; S<sup>2-<&sol;sup>&lpar;aq&rpar; PbS&lpar;s&rpar;<&sol;p>&NewLine;<p>Fe<sup>2&plus;<&sol;sup>&lpar;aq&rpar; &plus; S<sup>2-<&sol;sup>&lpar;aq&rpar; FeS&lpar;s&rpar;<&sol;p>&NewLine;<p>Most sulphides are insoluble in water except those of sodium&comma; potassium and ammonium&period; When equal volumes of equimolar hydrogen sulphide and sodium hydroxide solutions are reacted&comma; sodium hydrogen sulphide&comma; an acid salt is formed&period;<&sol;p>&NewLine;<p>NaOH&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;aq&rpar; NaHS&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p>When excess sodium hydroxide is used sodium sulphide&comma; a normal salt is formed&period;<&sol;p>&NewLine;<p>2NaOH&lpar;aq&rpar; &plus; H<sub>2<&sol;sub>S&lpar;aq&rpar;  Na<sub>2<&sol;sub>S&lpar;aq&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar;<&sol;p>&NewLine;<p><strong> <&sol;strong><&sol;p>&NewLine;<h1><a name&equals;"&lowbar;Toc51750112"><&sol;a>Pollution of the Atmosphere by Compounds of Sulphur<&sol;h1>&NewLine;<p>Sulphur compounds especially sulphur&lpar;IV&rpar; oxide and hydrogen sulphide&comma; are among the major atmospheric pollutants&period; Sulphur&lpar;IV&rpar; oxide is usually emitted into the atmosphere when sulphur containing fuels are burnt&period; Some sulphur&lpar;IV&rpar; oxide is also emitted during the extraction of metals such as copper and in the manufacture of sulphuric&lpar;VI&rpar; acid&period; In the atmosphere sulphur&lpar;IV&rpar; oxide dissolves in water to form sulphuric&lpar;IV&rpar; acid&period;<&sol;p>&NewLine;<p>SO<sub>2<&sol;sub>&lpar;g&rpar; &plus; H<sub>2<&sol;sub>O&lpar;l&rpar;  H<sub>2<&sol;sub>SO<sub>3<&sol;sub>&lpar;aq&rpar;<&sol;p>&NewLine;<p>The sulphuric&lpar;IV&rpar; acid is then oxidised by atmospheric oxygen to sulphuric&lpar;VI&rpar; acid&comma; which comes down as acid rain or acid fog&period; These have serious environmental effects&period; These include&colon;<&sol;p>&NewLine;<ul>&NewLine;<li>Stunted growth in plants due to loss of chlorophyll from plants&&num;8217&semi; leaves&period;<&sol;li>&NewLine;<li>Death of plants as a result of defoliation&period;<&sol;li>&NewLine;<li>Destruction of aquatic life in acidified lakes&period;<&sol;li>&NewLine;<li>Corrosion of stone work on buildings&period;<&sol;li>&NewLine;<li>Corrosion of metallic structures&period;<&sol;li>&NewLine;<li>Leaching of minerals in the soil&period;<&sol;li>&NewLine;<li>Irritation of the respiratory system<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<h1>Review Exercises<&sol;h1>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol>&NewLine;<li>2006 Q 6<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>In an experiment to study the properties of concentrated sulphuric acid&comma; a mixture of the acid and wood charcoal was heated in a boiling tube&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Write the equation of the reaction that took place in the boiling tube&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Using oxidation numbers&comma; show that reduction and oxidation reactions took place in the boiling tube&period;                                                 &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"2">&NewLine;<li>2006 Q 16<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>When hydrogen sulphide gas was bubbled into an aqueous solution of iron &lpar;III&rpar; chloride&comma; a yellow precipitate was deposited&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>State another observation that was made&period;          &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Write an equation for the reaction that took place&period;           &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>What type of reaction was undergone by hydrogen by hydrogen sulphide in this reaction&quest;                                                                                                                                      &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"3">&NewLine;<li>2006 Q 27 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Study the flow chart below and answer the questions that follow&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Name reagent z&period;                                                                              &lpar;1mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Describe the process which takes place in step 2&period;             &lpar;1mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Identify the white solid&period;             &lpar;1mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"4">&NewLine;<li>2006 Q 4 P2<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>The diagram below shows some processes that take place during the industrial manufacture of sulphuric acid&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Write the equation for the reaction in which sulphur dioxide gas is produced&period;                                         &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Why is it necessary to keep the gases pure and dry&quest;     &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Describe the process that takes place in chamber G&period;     &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Name the gases that escape into the environment&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>State and explain the harmful effect on the environment of one of the gases named in &lpar;iv&rpar; above                             &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Give one reason why it is necessary to use a pressure of 2-3 atmospheres and not more&period;             &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>&lpar;i&rpar; Complete the table below to show the observations made when concentrated sulphuric acid is added to the substances shown&period;      &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<table width&equals;"518">&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"235">Substance<&sol;td>&NewLine;<td width&equals;"283">                         Observation<&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"235">Iron fillings<&sol;td>&NewLine;<td width&equals;"283">&nbsp&semi;<&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"235">Crystals of white sugar<&sol;td>&NewLine;<td width&equals;"283">&nbsp&semi;<&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&lpar;ii&rpar; Give reasons for the observations made using&colon;<&sol;p>&NewLine;<ol>&NewLine;<li>iron fillings  &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Crystals of white sugar&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Name one fertilizer made from sulphuric acid&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Suggest a reason why BaSO<sub>4<&sol;sub>&lpar;a pigment made from sulphuric acid&rpar; would be suitable in making paint for cars&period;                                  &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"5">&NewLine;<li>2007 Q 30 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Below is a sketch of a graph showing the change in viscosity&quest; &lpar;Ease of flow&rpar; with temperature when solid sulphur is heated&period;<&sol;p>&NewLine;<p>Describe what happens to the sulphur molecules when sulphur is heated from 150 °C to about 200 °C&period;                                                                                                           &lpar;2 marks&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"6">&NewLine;<li>2008 Q 8 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>State the observation made at the end of the experiment when a mixture of iron powder and sulphur is heated in a test tube&period;                                &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Write an equation for the reaction the product in &lpar;a&rpar; above and dilute hydrochloric acid&period;                                           &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>When a mixture of iron powder and sulphur is heated&comma; it glows more brightly than that of iron fillings and sulphur&period; Explain this observation&period;                               &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"7">&NewLine;<li>2008 Q 9 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Zinc reacts with both concentrated and dilute sulphuric &lpar;VI&rpar; acid&period; Write equations for the two reactions&period;                                                                                                         &lpar;2 marks&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"8">&NewLine;<li>2008 Q 30 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Crude oil contains sulphur&period;  What would be the effect to the environment of using fuel containing sulphur&quest;                                                                                                             &lpar;1 mark&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"9">&NewLine;<li>2009 Q 22 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>A student added very dilute sulphuric &lpar;VI&rpar; acid to four substance and recorded the observations shown in the table below&period;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<table width&equals;"438">&NewLine;<tbody>&NewLine;<tr>&NewLine;<td width&equals;"114"><strong>Test <&sol;strong><&sol;td>&NewLine;<td width&equals;"162"><strong>Substance <&sol;strong><&sol;td>&NewLine;<td width&equals;"162"><strong>Gas given off <&sol;strong><&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"114">1<&sol;td>&NewLine;<td width&equals;"162">Sodium<&sol;td>&NewLine;<td width&equals;"162">Yes<&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"114">2<&sol;td>&NewLine;<td width&equals;"162">Iron<&sol;td>&NewLine;<td width&equals;"162">No<&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"114">3<&sol;td>&NewLine;<td width&equals;"162">Carbon<&sol;td>&NewLine;<td width&equals;"162">Yes<&sol;td>&NewLine;<&sol;tr>&NewLine;<tr>&NewLine;<td width&equals;"114">4<&sol;td>&NewLine;<td width&equals;"162">Copper<&sol;td>&NewLine;<td width&equals;"162">No<&sol;td>&NewLine;<&sol;tr>&NewLine;<&sol;tbody>&NewLine;<&sol;table>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>For which tests are the observations wrong&quest; Explain&period;                          &lpar;3 marks&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"10">&NewLine;<li>2010 Q 11 P1 &comma;2016 Q26 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Hydrogen sulphide is a highly toxic and flammable gas&period; It is normally prepared in a fume chamber&period;<&sol;p>&NewLine;<ul>&NewLine;<li>Name two reagents that can be used to prepare hydrogen sulphide in the laboratory&period;                             &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>One of the uses of hydrogen sulphide is to produce sulphur as shown in the following equation&semi;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p><strong>2H<sub>2<&sol;sub>S&lpar;g&rpar; &plus; SO<sub>2<&sol;sub>&lpar;g&rpar; <&sol;strong><strong>  3S&lpar;s&rpar; &plus; 2H<sub>2<&sol;sub>O&lpar;l&rpar; <&sol;strong><&sol;p>&NewLine;<p>Identify the reducing agent in this reaction and give a reason for your answer&period;                                                                                                                                                      &lpar;1 mark&rpar;<&sol;p>&NewLine;<ul>&NewLine;<li>Other than production of sulphuric &lpar;IV&rpar; acid&comma; state one commercial use of sulphur&period;                             &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"11">&NewLine;<li>2011 Q 17 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>The set up below was used to prepare a gas and study some of its properties&period;<&sol;p>&NewLine;<p>Study it and answer the questions that follow&colon;<&sol;p>&NewLine;<ul>&NewLine;<li>State and explain the observations made in the&period;&NewLine;<ol>&NewLine;<li>tube labelled A&semi;    &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>beaker labelled B&period;                                                                   &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ol>&NewLine;<&sol;li>&NewLine;<li>State <strong>one<&sol;strong> precaution that should be taken when carrying out this experiment&period;                                         &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"12">&NewLine;<li>2011 Q 1 P2<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>The flow chart below shows some of the processes involved in large scale production of sulphuric &lpar;VI&rpar; acid&period; Use it to answer the questions that follow&period;<&sol;p>&NewLine;<ul>&NewLine;<li>Describe how oxygen is obtained from air on a large scale&period;               &lpar;3 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>&lpar;i&rpar; Name substance <strong>A<&sol;strong>&period;                                                                                  &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&lpar;ii&rpar; Write an equation for the process that takes place in the absorption<&sol;p>&NewLine;<p>chamber                                                                                                          &lpar;1 mark&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Vanadium &lpar;V&rpar; Oxide is a commonly used catalyst in the contact process&period;<&sol;li>&NewLine;<li>Name another catalyst which can be used for this process&period;                       &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Give <strong>two<&sol;strong> reasons why vanadium &lpar;V&rpar; Oxide is the commonly used catalyst&period;                                                                                                                                             &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>State and explain the observation made when concentrated sulphuric acid is added to crystals of copper &lpar;II&rpar; sulphate in a beaker&period;                            &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>The reaction of concentrated sulphuric &lpar;VI&rpar; acid with sodium chloride produces hydrogen chloride gas&period; State the property of concentrated sulphuric &lpar;VI&rpar; acid illustrated in this reaction&period;                                                                                              &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Name <strong>four<&sol;strong> uses of sulphuric &lpar;VI&rpar; acid&period;                                              &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"13">&NewLine;<li>2012 Q18 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Acidified potassium manganate &lpar;VII&rpar; solution is decolourised when sulphur &lpar;IV&rpar; oxide is bubbled through it&period; The equation for the reaction is given below&period;<&sol;p>&NewLine;<p><strong> 2H<sub>2<&sol;sub>O &lpar;l&rpar; &plus; 5SO<sub>2<&sol;sub>&lpar;g&rpar; &plus;2KMnO<sub>4<&sol;sub>&lpar;aq <&sol;strong><strong> K<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq&rpar; &plus; 2MnSO<sub>4<&sol;sub>&lpar;a &plus; 2H<sub>2<&sol;sub>SO<sub>4<&sol;sub>&lpar;aq<&sol;strong>&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Which reactant is oxidised&quest; Explain&period;                                                                  &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Other than the manufacture of sulphuric &lpar;VI&rpar; acid&comma; state other use of sulphur &lpar;IV&rpar; oxide                                                                                                                                &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"14">&NewLine;<li>2013 Q12 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>What would be observed if sulphur &lpar;IV&rpar; oxide is bubbled through acidified potassium manganate&lpar;VII&rpar;&quest;                   &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>In an experiment&comma; sulphur &lpar;IV&rpar; oxide was dissolved in water to form solution <strong>L<&sol;strong>&period;<&sol;li>&NewLine;<li>What would be observed if a few drops of barium nitrate solution were <strong>immediately<&sol;strong> added to solution <strong>L<&sol;strong>&quest;                                                                                   &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Write an ionic equation for the reaction that occurred between solution <strong>L<&sol;strong> and aqueous barium nitrate in &lpar;b&rpar; &lpar;i&rpar; above&period;                                                                      &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"15">&NewLine;<li>2013 Q3 P2&NewLine;<ul>&NewLine;<li>The diagram below shows the Frasch process used for extraction of sulphur&period; Use it to answer the question that follows&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>Identify X&period;                                                                                                       &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Why is it necessary to use superheated water in this process&quest; &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>State two physical properties of sulphur that makes it possible for it to be extracted by this method&period;                                       &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>The diagram below shows part of the process in the manufacture of sulphuric &lpar;VI&rpar; acid&period; Study it and answer the questions that follow&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Write an equation for the formation of sulphur &lpar;IV&rpar; oxide from sulphur&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>What is the role of concentrated sulphur &lpar;VI&rpar; acid in chamber A&quest;            &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Name two catalysts that can be used in the catalytic chamber B&period;            &lpar;2 marks&rpar;<&sol;li>&NewLine;<li>State two roles of the heat exchanger&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Explain one way in which sulphur &lpar;IV&rpar; oxide is a pollutant                                           &lpar;1mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>What observation will be made when a few drops of concentrated sulphuric &lpar;VI&rpar; acid are added to crystals of sugar&quest; Explain your answer&period;                                                                       &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"16">&NewLine;<li>2014 Q11 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Study the flow chart below and answer the questions that follow&period;<&sol;p>&NewLine;<p>Identify Z and M&period;                                                                                                         &lpar;2 marks&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"17">&NewLine;<li>2014 Q20 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>In the contact process&comma; during the production of sulphur &lpar;VI&rpar; oxide&comma; a catalyst is used&period; Give two reasons why vanadium &lpar;V&rpar; oxide is preferred to platinum&period;                                                                                                                                                                                               &lpar;2 marks&rpar;<&sol;p>&NewLine;<ol start&equals;"18">&NewLine;<li>2015 Q17 P1<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>One of the allotropes of sulphur is rhombic sulphur&comma; name the other allotrope&period;                                                                                                                                                                   &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Concentrated sulphuric &lpar;VI&rpar; acid reacts with ethanol and copper&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>State the property of the acid shown in each case&period;                                       &lpar;2 marks&rpar;<&sol;p>&NewLine;<ul>&NewLine;<li>Ethanol<&sol;li>&NewLine;<li>Copper &&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&&num;8230&semi;&period;&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"19">&NewLine;<li>2015 Q5 P2<&sol;li>&NewLine;<&sol;ol>&NewLine;<ul>&NewLine;<li>The set up below can be used to generate a gas without heating&period; This occurs when substance M reacts with solid N&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Complete the table below giving the names of substance M and solid N if the gasses generated are chlorine and sulphur &lpar;IV&rpar; oxide&period;                                &lpar;2 marks&rpar;<&sol;li>&NewLine;<li>Complete the diagram above to show how a dry sample of sulphur &lpar;IV&rpar; oxide can be collected&period;              &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Describe two chemical methods that can be used to test the presence of sulphur &lpar;IV&rpar;oxide&period;                                  &lpar;3 marks&rpar;<&sol;li>&NewLine;<li>Other than the manufacture of sulphuric &lpar;VI&rpar; acid&comma; state two uses of sulphur &lpar;IV&rpar; oxide&period;                                                                                                                                   &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"20">&NewLine;<li>2017 P1 Q7&period;<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>A sample of water is suspected to contain sulphate ions&period; Describe an experiment that can be carried out to determine the presence of sulphate ions&period;                                      &lpar;3 marks&rpar;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"21">&NewLine;<li>2017 P2 Q3 &lpar;a&rpar;<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>A student used <strong>Figure 2<&sol;strong> to investigate the action of dilute sulphuric &lpar;VI&rpar; acid on some metals&period;<&sol;p>&NewLine;<p>Beaker <strong>I<&sol;strong> and <strong>II <&sol;strong>contained equal volumes of dilute sulphuric &lpar;VI&rpar; acid&period; To beaker <strong>I<&sol;strong>&comma; a clean iron rod was dipped and to beaker <strong>II<&sol;strong>&comma; a clean copper rod was dipped&period;<&sol;p>&NewLine;<ul>&NewLine;<li>Why was it necessary to clean the metal rods&quest;          &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Describe the observations made in each beaker&period;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>Beaker I&colon;                                                                                                         &lpar;1 mark&rpar;<&sol;p>&NewLine;<p>Beaker II&colon;                                                                                                        &lpar;1 mark&rpar;<&sol;p>&NewLine;<ul>&NewLine;<li>Explain the observations in &lpar;a&rpar; &lpar;ii&rpar;&period;          &lpar;2 marks&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"22">&NewLine;<li>2018 P1 Q 4&period;<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>One of the allotropes of sulphur is rhombic sulphur&period;<&sol;p>&NewLine;<ul>&NewLine;<li>Name the other allotrope of sulphur&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ul>&NewLine;<li>Draw a diagram to show the shape of the allotrope named in &lpar;a&rpar; above&period;                               &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Write an equation for the reaction between concentrated sulphuric&lpar;VI&rpar; acid and sulphur&period;                                           &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<p>&nbsp&semi;<&sol;p>&NewLine;<ol start&equals;"23">&NewLine;<li>2019 P1 Q9&period;<&sol;li>&NewLine;<&sol;ol>&NewLine;<p>Sulphur&lpar;IV&rpar; oxide is prepared in the laboratory using the set-up in <strong>Figure 3&period;<&sol;strong><&sol;p>&NewLine;<p>Study it and answer the questions that follow&period;<&sol;p>&NewLine;<ul>&NewLine;<li>Identify substance F&period; &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>Write an equation for the reaction that takes place in the flask&period;          &lpar;1 mark&rpar;<&sol;li>&NewLine;<li>State the purpose of liquid G&period;                                                             &lpar;1 mark&rpar;<&sol;li>&NewLine;<&sol;ul>&NewLine;

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