Sulphur, Hydrogen Sulphide

I. Give scientific reasons 1. Powdered sulphur is dusted on fruit trees. 1. Sulphur is fungicide as well as insecticide. 2. Hence for killing bacteria, fungi and other germs on the fruit trees, powdered sulphur is dusted over them. 2. Sulphur exists in two crystalline forms. 1. The most stable form of sulphur is rhombic sulphur. 2. The molecules of rhombic sulphur are closely packed. 3. Above 95.50 C., the intermolecular attraction weakens and they rearrange to form new crystalline allotrope of sulphur monoclinic sulphur. Hence, sulphur exists in two crystalline forms. 3. An ignited magnesium wire continues to burn in jar or sulphur dioxide. (T.B) Ans. 1. Magnesium is a strong reducing agent. 2. It burns in sulphur dioxide and reduces it to yellow particles, which are left behind. 3. It is an exothermic reaction. Hence, an ignited magnesium wire continues to burn in a jar of sulphur dioxide. 2Mg + SO2 2 MgO + S 4. Sulphur dioxide is used in sugar industry. Sulphur dioxide is used to bleach silk and woolen clothes. Ans. 1. Sulphur dioxide is a mild bleaching agent. 2. It is harmless and not so poisonous. 3. It releases nascent hydrogen when dissolved in water, which bleaches sugar by reduction. Hence, sulphur dioxide is used in sugar industry. (or) Sulphur dioxide is used to bleach silk and woolen clothes. 5. When hydrogen Sulphide gas is passed through acidified solution of sulphate, a black precipitate is formed. Ans. When hydrogen Sulphide gas is passed through acidified solution of copper sulphate, a black precipitate is formed due to the formation of black insoluble precipitate of copper Sulphide. CuSO4 + H2S CuS + H2SO4

6. Acidified potassium dichromate solution turns green when hydrogen Sulphide gas is passed through it. Ans. When hydrogen Sulphide gas is passed through acidified solution of potassium dichromate, it reduces to potassium sulphate and chromium sulphate. Potassium sulphate is colourless, while chromium sulphate is green in colour. K2Cr2O7

+

3H2SO4

+

3H2S

K2SO4 + Cr (SO4)3 + 7H2O + 3S

7. Acidified of potassium permanganate (KMnO4) solution turns colourless when hydrogen Sulphide gas is passed through it. Ans. When hydrogen Sulphide gas is passed through acidified solution of potassium permanganate the purple solution turns colourless due to the formation of potassium sulphate and manganese sulphate. 2KMnO4 + 3H2SO4 + 5H2S

K2SO4 + 2MnSO4 + 8H2O + 5S

8. A lump of sulphur when rubbed against dry hand or wool attracts scraps of paper. Ans. 1. When a lump of sulphur is rubbed against dry hand or wool, its surface becomes electro statically charted. Hence, it attracts scraps of paper. 9. Vulcanised rubber is used to make tubes and tyres of vehicles. Ans. 1. Raw natural rubber is soft and sticky. 2. In the vulcanisation, this rubber is heated with sulphur. 3. Vulcanised rubber is hard and tough, Hence vulcanised rubber is used to make tubes and tyres of vehicles. 10. It is dangerous to smell sulphur dioxide. Ans. 1. Sulphur dioxide gas has an extremely pungent and strongly suffocating odour. 2. It is poisonous and causes inflammation of lungs. Hence, it is dangerous to smell sulphur dioxide. II. Answer the following short: 1. Name the ores of Sulphur. Ans. The ores of sulphur are: 1. Cinnabar {Hgs} 3. Iron Pyrites {FeS2} 5. Copper Pyrites {CuFeS2} 7. Kieserite {MgSO4. H2O}

2. Zincblende {Zns} 4. Galena (PbS) 6. Gypsum {CaSO4. 2H2O} 8. Anglesite (PbSO4)

2. Explain the position of sulphur in the periodic table. Ans. The atomic number of sulphur is 16. Its electronic configuration is 2,8,6. It has 6 electrons in its outer orbit. Hence sulphur is placed in VI – A group and third period of the modern periodic table below the oxygen.

3. Explain the effect of heat on sulphur at different temperatures. At the following temperature, state the changes in the condition of sulphur. i. 119.2oC ii. 160 oC iii. 300 oC iv. 444 oC Ans. When sulphur is heated, the following changes are observed. 1. The yellow solid melts at 119.2 oC and a clear amber coloured, free flowing liquid is formed. 2. When the temperature rises, the liquid progressively darkens. At about 160 oC , it becomes almost black and highly viscous. It does not flow out even when the test rube is inverted. 3. On heating further, at about 300 oC, Sulphur gradually becomes less viscous and starts flowing freely. Its colour is dark reddish brown. 4. At 444 oC, Sulphur boils, giving out light orange coloured sulphur vapour. 4. What is vulcanisation of rubber? Ans. 1. The process of heating raw rubber with sulphur at a definite temperature for a definite time is called vulcanisation. 2. It is used to convert soft, sticky mass of rubber into hard, tough mass i.e., in the manufacture of tyres.

5. Give the uses of sulphur in agriculture. Ans. 1. Sulphur dust is sprayed on fruit trees and grape vines to destroy insects and fungi harmful to these plants. 2. Sulphur is used in the preparation of various insecticides and pesticides. 6. Give the uses of sulphur in medicines. Ans. 1. Sulphur is used in skin ointments for skin diseases. 2. Metal Sulphide are used as medicines. 3. Sulpha drugs contain sulphur. 4. Sulphur in the form of minute particles is used in oral medicines.

7. Give the important uses of sulphur{OR} Write the uses of sulphur in 1. Chemical industry. 2. Agricultural 3. Vulcanisation Ans. Uses of sulphur are_ 1. In chemical Industry: It is used in the manufacture of sulphur dioxide, sulphuric acid, carbon disulphide and metal Sulphide. 2. Vulcanisation:- The process of heating raw rubber with sulphur at a definite temperature for a definite time is called vulcanisation. It is used to convert soft, sticky mass of rubber into hard, tough mass i.e., in the manufacture of tyres. 3. In agriculture: It is used as an insecticide and fungicide and sprayed on fruit trees and grape vines. 4. In medicine: It is used in skin ointments. 5. It is used as an ingredient of gunpowder. 8. What are the components of gunpowder? Ans. Gun powder contains sulphur, Charcoal and nitre (Potassium Nitrate) 9. State the uses of sulphur (or) Sulphur in Chemical industries. Ans. The uses of sulphur as follows: 1. It is used in preparing sulphuric acid. 2. It is used to produce sulphur dioxide, which is used in bleaching straw and wool. 3. Sulphur produces carbon disulphide, which is used as an industrial solvent. 4. It is used in gunpowder as an ingredient. Gunpowder contains sulphur, Charcoal and nitre (Potassium Nitrate). 5. It is used in fire works. 6. It is used in Crackers. 7. It is used as in insecticide for fruit trees. 8. It is used to prepare different pesticides. 9. It is used in ointments for skin diseases. 10. It is used in the process of vulcanisation to give toughness to rubber. 11. It is used in prepare different Sulphide. 10. State the physical properties of Sulphur. Ans. The physical properties of sulphur are as follows. 1. Sulphur is a hard, yellow, brittle solid. 2. Its melting point is 119.2 oC

3. It is tasteless and odourless. 4. It is insoluble in water, liberally soluble in alcohol and ether and easily soluble in carbon disulphide and carbon tetrachloride. 5. It is a poor conductor of heat and electricity. 6. A lump of sulphur when rubbed against dry hand or against wool becomes electro statically charged and attracts scraps of paper. 11. State the physical properties and uses of hydrogen Sulphide. Ans. The physical properties hydrogen Sulphide are as follows_ 1. It is colourless gas. 2. It has an odour of rotten egg. 3. It is heavier than air and moderately soluble in water. The uses of hydrogen Sulphide are as follows. 1. It is used as a laboratory reagent to detect the basic radicals of the salts. 2. It is used as a reducing agent. 12. Explain the bleaching action of sulphur dioxide. (T.B) Ans. When Sulphur dioxide id dissolved in water produces sulphuric acid and nascent hydrogen. Nascent hydrogen bleaches colouring matter. Thus, sulphur dioxide acts as a bleaching agent. SO2 + H2O H2SO3 (Sulphuric acid) H2SO3 + H2O H2SO4 + 2H (Nascent) Colouring matter + 2H (Nascent) Colourless matter. 13. Give the physical properties of Sulphur dioxide. Ans. The physical properties of sulphur dioxide are as follows. 1. It is a colourless gas. 2. It has a strong suffocating odour. 3. It is fairly soluble in water but escapes on warming the solution. 4. It is poisonous and harmful to plants. 5. At ordinary temperature it can be liquefied at a pressure of three atmosphere. 6. It is about 2.2 times as heavy as air. 14. Give the uses of Sulphur dioxide. Ans. The uses of sulphur dioxide are as follows. 1. It is used in the manufacture of sulphuric acid. 2. It is used for bleaching sugar, synthetic fibres etc. 3. It is used in the manufacture of compounds like calcium bisulphate, which is useful in paper industry. 4. Liquid sulphur dioxide is used in purifying petroleum and as a solvent. 5. It is used as a disinfectant. 6. It is used as a preservative for dried fruits.

7. It is used in household refrigerators. 15. Sulphur is used in explosive Ans. Sulphur forms an explosive mixture with potassium chlorate. It detonates when heated or struck. Hence, sulphur is used in explosives. 16. The effect of heat on sulphur is reversible. Ans. 1. Rhombic sulphur is the most stable form of sulphur. 2. When it is heated, gradually different structural changes take place. 3. The changes occur in the reverse order when boiling sulphur is cooled. Hence, the effect of heat on sulphur is reversible. 17. A moistened coloured flower turns colourless in a jar containing sulphur dioxide. OR. Explain the bleaching action of sulphur dioxide on flowers. Ans. 1. When a coloured flower is introduced in a gas jar containing sulphur dioxide, the gas reacts with water present in the flower itself producing nascent hydrogen. 2. This hydrogen reduces the colouring matter in the flower to colourless substances. Hence, the flower losses its colour in the gas jar. 18. Sulphur dioxide is used for bleaching woolen and silk garments. Ans. Sulphur dioxide is a mild bleaching agent. 1. Sulphur dioxide reacts with water producing nascent hydrogen. 2. Nascent hydrogen reduces the colouring matter. 3. This bleaching action is a mild action. 4. As wool and silk fibres are synthetic fibres and are quite delicate, stronger reducing agents like chlorine affects the strength of the fibres and make it weak. Hence, for their bleaching sulphur dioxide is used. 19. Sulphur dioxide gas is used extensively in textile and paper industries. Ans. Sulphur dioxide is a mild bleaching agent. 1. Sulphur dioxide reacts with water producing nascent hydrogen. 2. Nascent hydrogen reduces the colouring matter. 3. This bleaching action is a mild action.

4. In textile and paper industries sulphur dioxide is used to decolourise the fabric and paper pulp, respectively. Hence, sulphur dioxide is used extensively in textile and paper industries. 20. Sulphur dioxide is used in sugar industry. Ans. Sulphur dioxide is a mild bleaching agent. 1. Sulphur dioxide reacts with water producing nascent hydrogen. 2. Nascent hydrogen reduces the colouring matter. 3. This bleaching action is a mild action. 4. Moreover, it is not so poisonous like chlorine, which is also a bleaching agent. 5. For bleaching sugar extract, a mild and harmless bleaching agent is required. Hence, sulphur dioxide is used to bleach sugar solution in sugar industry.

21. Acidified potassium permanganate solution becomes colourless when sulphur dioxide is passed through it. Ans. 1. Sulphur dioxide is a reducing agent. 2. Potassium permanganate is violet in colour. 3. When sulphur dioxide is passed through an acidified solution of potassium permanganate, the latter is reduced to colourless potassium sulphate and colourless manganese sulphate. Hence, the solution becomes colourless. 22. Acidified potassium dichromate solution turns green when sulphur dioxide is passed through it. Ans. 1. Sulphur dioxide is a reducing agent. 2. Potassium dichromate is orange in colour. 3. When sulphur dioxide is passed through an acidified solution of potassium dichromate, the latter is reduced to colourless potassium sulphate and green chromium sulphate. Hence, the solution turns green.

III. Preparation of gases. 1. In the preparation of hydrogen Sulphide gas in the laboratory. (T.B) i. State the chemical used. ii. Give balanced chemical equation for the preparation. iii. Name the methods of collection of gas. Ans.

1. Iron Sulphide and dilute sulphuric acid or dilute hydrochloric acid are the chemicals used. 2. FeS+ H2SO4 FeSO4 + H2S FeS+ 2HCl FeCl2 + H2S 3. Hydrogen Sulphide is collected by upward displacement of air. 2. In the preparation of sulphur dioxide gas i. State the chemicals used. ii. Give Balanced Chemical equations. iii. State the method of collection. Ans.

1. Copper turnings and concentrated sulphuric acid are the chemicals used. 2. Cu + 2 H2SO4 heat CuSO4 + 2H2O SO2 3. Sulphur dioxide is collected by Upward displacement of air.

IV. Distinguish between 1. Rhombic sulphur and Monoclinic sulphur. Rhombic sulphur 1. The crystals of rhombic sulphur are rhombic. 2. It is the most stable allotrope of sulphur at normal temperature. 3. It is opaque. 4. It is converted into monoclinic sulphur when heated above 95.50C

Monoclinic Sulphur 1. The crystals of monoclinic sulphur are monoclinic or needle shaped. 2. It is stable only above 95.50C 3. It is transparent. 4. It is converted into rhombic sulphur when cooled below 95.50C.

2. Rhombic sulphur and Plastic Sulphur. Rhombic sulphur 1. Rhombic sulphur is a crystalline allotrope of sulphur. 2. The crystals of rhombic sulphur are rhombic. 3. It is not plastic. It is brittle. 4. It is pale yellow. 5. It is the most stable allotrope of sulphur. 6. It is soluble in carbon disulphide.

Plastic sulphur 1. Plastic sulphur is an amorphous allotrope of sulphur. 2. Plastic sulphur has no specific shape. 3. It is plastic and sticky. 4. It is brown – Black. 5. It is unstable and at room temperature, it is slowly converted into rhombic sulphur. 6. It is insoluble in carbon disulphide.

3. Monoclinic sulphur and Plastic sulphur. Monoclinic sulphur 1. Monoclinic sulphur is a crystalline allotrope of sulphur. 2. The crystals of monoclinic sulphur are needle – shaped. 3. It is not plastic. It is brittle. 4. It is pale yellow. 5. It is soluble in carbon disulphide. 6. It is stable only above 95.50C

Plastic sulphur 1. Plastic sulphur is an amorphous allotrope of sulphur. 2. Plastic sulphur has no specific shape. 3. It is plastic. 4. It is brown – black. 5. It is insoluble in carbon disulphide. 6. It is slowly converted into rhombic sulphur at a normal temperature.