Cq Fossil Fuels

Fossil Fuels

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Fossil Fuels : 1983 2. (c) Bromotrifluoromethane (abbreviated as B.T.M.) is a substituted methane and exists as a gas at room temperature and pressure. It is used by the Mass Transit Railway to extinguish fires caused by electrical faults. (i)* Write the structural formula and draw a three-dimensional diagram for a molecule of B.T.M. (ii) Calculate the density of B.T.M. (in g dm-3) at room temperature and pressure. (iii) If the density of air at room temperature and pressure is 1.18 g dm-3, calculate the ratio of the density of B.T.M. to that of air. (iv) Give two reasons why B.T.M. can be used for extinguishing fires caused by electrical faults. (Given : Relative atomic masses : C=12.0, F = 19.0, Br = 80.0; Molar volume of a gas at room temperature and pressure = 24.0 dm3) (8 marks) Fossil Fuels : 1985 5. (b) (i) Acid-rain is often associated with air pollution. Rain-water samples collected in some areas in Hong Kong have pH values as low as 5. (1) Name two gases which are the major cause of acid-rain, and suggest one source for each gas. (2) Write equations to show the reactions between rain-water and each of the two gases. (ii) Calcite (CaCO3) is present in some sedimentary rocks in Ping Chau. How would calcite be affected by acid rain? (iii)Which metal, iron or aluminium, is a more durable material for window frames ? Explain your answer. (7 marks) Fossil Fuels : 1986 4. (a) Coal and petroleum are fossil fuels formed from different organisms. (i) (1) What is coal formed from? (2) What is petroleum formed from? (ii) Name the process used in separating the different components in crude oil. (iii) Give one major use of the mixture of hydrocarbons having 5 to 10 carbon atoms per molecule, obtained from the process described in (ii). (iv) Lighter hydrocarbons can be obtained from heavier ones by a process called cracking, What are the conditions required for this process? (v) The reserve of fossil fuels is limited and is running out, Suggest two alternative energy sources. (vi) Give TWO pollution problems associated with oil spillage. (10 marks) 4. (b)

Fossil Fuels

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Two colourless gases, A and B, are both present in town gas. The following table shows the reaction between these two gases and oxygen : Reaction with oxygen Gas A Burns to form gas C and water. Gas B Burns to form gas C only. Gas C can turn limewater milky. (i) What is gas C ? Write a balanced equation to show its reaction with limewater. (ii) Do you think hydrogen is present in molecules of gas A ? Explain your answer. (iii) It was found that two moles of gas B required one mole of oxygen for complete combustion to form two moles of gas C. From this information, deduce what gas B is. (iv) Gas B is an air pollutant. (1) Suggest a major source of this pollutant. (2) Explain how it affects the normal functioning of blood. (v) Give one safety precaution necessary when using town gas. (8 marks) 2. (c) In some cities, the air is often polluted by oxides of nitrogen. (i) Name an oxide of nitrogen that causes air pollution. (ii) Briefly explain how nitrogen oxides may be formed (1) in cities with heavy traffic, and (2) in nature. (iii)Suggest TWO harmful effects of nitrogen oxides in the atmosphere. (6 marks)

Fossil Fuels : 1988 5. (b) Long chain molecules obtained from the fractional distillation of crude oil can be converted to smaller molecules by the process of cracking. One example is illustrated by the equation below : C10H22 → A + B where A is a saturated hydrocarbon containing 7 carbon atoms, and B is an unsaturated hydrocarbon. (i) Why is cracking important in the petroleum industry ? (ii) Write the molecular formula of A. (iii)(1) Explain the term "unsaturated hydrocarbon" (2) Write the structural formula of B. (3) Give one use of B. (iv) Suggest a chemical test to distinguish P from A, and write an appropriate equation. (v) Predict whether A or B would have the higher boiling point and explain your answer. (9 marks) Fossil Fuels : 1989

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5. (b) Two experiments were performed using the following set-up : Experiment I II

Liquid used to soaked the rocksil kerosene ethanol

(i) Name the type of reaction involved in (1) Experiment I, (2) Experiment II. (ii) After reaction, a thin layer of oily liquid appeared in the beaker of water in Experiment I, but not in Experiment II. (1) Suggest what this oily liquid might be. (2) Explain why no oily liquid was formed in Experiment II. (iii) Under what circumstance would sucking back occur in both experiments ? (iv) The colourless gaseous products in both experiments can decolorize bromine water. What conclusion can be drawn about the nature of these gases ? (v) Explain why the process represented by Experiment I is important industrially. Suggest TWO uses of the products from the industrial process. (8 marks)

Fossil Fuels : 1990 3. (a) Hong Kong imports naphtha (mainly C5H12), from which town gas is produced. (i) What is the raw material from which naphtha is obtained? How is naphtha obtained from this raw material? (ii) Town gas is produced by reacting naphtha with steam. Write an equation for this reaction. Name two major components in town gas. (iii)What is observed when town gas is passed through a sample of citrated blood? Explain your answer. (iv) What is observed when town gas is gassed over heated copper(II) oxide in a combustion tube? Explain your answer and write appropriate equations. (v) State TWO potential hazards associated with the use of town gas. (vi) If you suspect there is a leakage of town gas in your home, explain why (1) you should open all the windows at once. (2) you should NOT use your telephone to call for help. (13 marks) Fossil Fuels : 1991 3. (a)

Fossil Fuels

Petroleum, often referred to as a 'fossil' fuel, can be separated into various fractions by fractional distillation. The following table shows the annual production and consumption of petroleum fractions in a certain country.

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Petroleum fraction

Annual production (in million tonnes) 10 5 20 15 40 6

Annual consumption (in million tonns) 25 5 20 35 5 4

Petrol Naphtha Kerosene Diesel oil Heavy oil L. P. G. (i) Why is petroleum referred to as a 'fossil' fuel ? (ii) Why can the various petroleum fractions be obtained from petroleum by fractional distillation ? (iii) According to the above table, some fractions are produced in excess while some others are not sufficient to meet the annual consumption requirements. (1) Identify a fraction that is produced in excess and cap be converted into those which are not sufficient. (2) Suggest a chemical method for the above conversion. (iv) A sample of liquefied petroleum gas is known to contain propene and propane. (1) Draw the structural formula of (I) propene, and (II) propane. (2) (I) Write the equation for the complete combustion of propane in air. (II)*Explain whether the combustion of propene or propane would produce a more sooty flame. (3) How would you show that propane consists of (I) carbon, and (II) hydrogen ? (4) Apart from combustion, describe another chemical test to distinguish propene from propane. (13 marks)

Fossil Fuels : 1992 1. (c) In motor car engines, petrol is mixed with air and burnt to produce power. (i) Using C8 H18 to represent petrol, write a balanced equation for the complete combustion of petrol. Explain why this reaction can produce power. (ii) What would happen if the supply of air is insufficient for the combustion of petrol in the car engine ? (4 marks) Fossil Fuels : 1993 1. (c) Alkenes can be obtained from petroleum fractions by a process called 'cracking'. Using a suitable petroleum fraction, a student carried out this process in the laboratory and collected the gaseous product over water.

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(i) What is 'cracking' ? Draw a labelled diagram of a laboratory set-up that can be used for carrying out the process and collecting the gaseous product, (iii) An important safety precaution in the experiment is to prevent sucking back. (1) What is the potential hazard if sucking back occurs ? (2) How can sucking back be prevented? (iv) If the gaseous product decolorizes a solution of bromine in trichloromethane, can you conclude that the gaseous product is ethene ? Explain your answer. (8 marks) Fossil Fuels : 1996 3. 'Fossil fuels' such as petroleum and coal constitute the world's major source of energy. However, many countries have been developing alternative energy sources. (a) Why are petroleum and coal called 'fossil fuels'? (b) Give TWO reasons why it is necessary to develop alternative energy sources. (c) Nuclear power is used as an alternative to fossil fuels in many countries. Suggest ONE advantage and ONE disadvantage of using nuclear power. (d) Suggest ONE energy source, other than nuclear power, that can he used as an alternative to fossil fuels. (6 marks) 9. (a) The diagram below shows a longitudinal section of a fire extinguisher. When the extinguisher is being used, solution X is allowed to mix with the sodium hydrogencarbonate solution and a reaction immediately occurs. A jet of aqueous solution will then be forced out of the extinguisher. (i) Suggest what solution X may be, (ii) (1) Write an ionic equation for the reaction between solution X and the sodium hydrogencarbonate solution . (2) Explain why a jet of aqueous solution is forced out of the extinguisher. (iii)The diagram below shows a 'fire triangle'. (1) Complete the 'fire triangle' by writing a suitable word for 'Y'. (2) Using the concept of fire triangle', give TWO reasons why the fire extinguisher mentioned previously can be used to put out a fire. (iv) In the Mass Transit Railway, bromochloro-difluoromethane (BCF) fire extinguisher, rather than the type of fire extinguisher shown on the previous page, is used to put out electrical fires, Suggest ONE advantage and ONE disadvantage of using a BCF fire extinguisher to put out electrical fires. (8 marks)

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Fossil Fuels : 1997 9. (a) The photograph below shows a gas burner with a can of fuel. The can contains 250 g of liquefied butane. (i) Write the structural formula of butane. (ii) (1) Write the chemical equation for the complete combustion of butane. (2) Suggest a chemical test for EACH of the products formed when butane is completely burnt in air. (3) Calculate the volume of the gaseous product formed, measured at room temperature and pressure, if all the butane contained in the can is completely burnt in air. (iii)Explain why it is dangerous to use such gas burners in a poorly-ventilated room. (RAM’s: H = 1.0, C = 12.0, O=16.0; molar volume of gas at room temperature and pressure = 24.0 dm3) (9 marks)

Fossil Fuels : 1998 4. On a hot summer day, the engine of a moving bus suddenly caught fire. When the firemen arrived, they used foam, instead of water, to put out the fire. After the fire was extinguished, the firemen sprayed a lot of water onto the hot engine. Discuss the conditions required for the fire to occur and explain the underlying principles of the actions taken by the firemen. (9 marks)

Fossil Fuels : 1999 3. The illustration below shows the exhaust from a motor car using unleaded petrol:

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Carbon monoxide, nitrogen oxides, particulates, …..

(a) Explain why the exhaust contains carbon monoxide. (b) (1) Write TWO chemical equations for the formation of acid rain from nitrogen oxides. (2) State ONE undesirable effect of acid rain. (c) State ONE health hazard associated with particulates. (d) Suggest ONE other pollutant that may be found in the exhaust. (e) Suggest a device that can be installed in the motor car to reduce the emission of carbon monoxide and nitrogen oxides. (7 marks) 9. (b) Cracking of naphtha gives alkane X (relative molecular mass 44), alkene Y (relative molecular mass 42) and other products. (i) (ii) (iii) (iv)

What is the meaning of the term ‘cracking’? Suggest a chemical test to distinguish between X and Y. Deduce the molecular formula of Y. Y can be used as a starting material for the production of plastic Z. (1) Write the chemical equation for the formation of Z from Y. (2) Suggest how plastic cups can be made from Z. (v) Suggest an advantage and a disadvantage of using plastic wastes as an energy source. (Relative atomic masses: H=1.0, C=12.0) (10 marks)

Fossil Fuels : 2000 6. (c) (i) In cold weather, a person trying to warm up a room with a coal fire soon gets dizzy. (2 marks)

Fossil Fuels

8. (a) Crude oil is a mixture consisting mainly of alkanes. Fractional distillation of crude oil gives different petroleum fractions. The table below lists the length of carbon chain of the alkanes in some of the fractions.

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Fraction Petrol/naphtha Kerosene Diesel X

Length of carbon chain C5 – C10 C11 – C18 C18 – C25 C20 – C34

(i) Describe the principle underlying the fractional distillation of crude oil. (ii) (1) Explain why the global demand for petrol is greater than that for kerosene. (2) Cracking kerosene can produce petrol. State the conditions required for the cracking process. (iii) In Hong Kong, naphtha instead of coal is used to manufacture town gas. (1) State ONE advantage of using naphtha instead of coal to manufacture town gas. (You are NOT required to consider the price of the materials.) (2) Explain why an additive with a foul smell is added to town gas before it is delivered to the consumers. (iv) Give ONE use of fraction X in cars. (9 marks) 9. (b) Carbon dioxide constitutes about 0.03% of the atmosphere. Over millions of years, the concentration of carbon dioxide in the atmosphere has remained almost constant because of a number of processes. (i) Suggest ONE process by which carbon dioxide is added to the atmosphere. (ii) Suggest ONE process by which carbon dioxide in the atmosphere is consumed. (iii) Carbon dioxide is one of the greenhouse gases in the atmosphere. (1) Explain why carbon dioxide can cause the greenhouse effect. (2) State the importance of the greenhouse gases in the atmosphere to living things on earth. (3) Increasing the concentration of the greenhouse gases in the atmosphere leads to global warming. State ONE harmful effect of global warming. (6 marks)