Beatty 18.1 Air WS1 Answers 1

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: _______________ Class: 4E1 TOPIC: AIR – ATMOSPHERE & ENVIRONMENT (WORKSHEET 1) Learning Objectives: (a) Describe the volume composition of gases present in dry air as being approximately 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide. (b) Name some common atmospheric pollutants, e.g. ca rbon monoxide; methane; nitrogen oxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons. (c) State the sources of these pollutants as: (i) carbon monoxide from incomplete combustion of carbon-containing substances (ii) nitrogen oxides from lightning activity and internal combustion engines (iii) sulfur dioxide from volcanoes and combustion of fossil fuels (d) Describe the reactions used in possible solutions to the problems arising from som e of the pollutants named (i) the redox reactions in catalytic converters to remove combustion pollutants, (ii) the use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation. (e) Discuss some of the effects of these pollutants on health and on the environment: (i) the poisonous nature of carbon monoxide (ii) the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’ and its effects on respiration and buildings. Multiple-Choice Questions 1 Which of the following noble gases has the highest percentage composition in the air? A argon B helium C neon D xenon ( A ) 2 Which of the following is obtained industrially from the fractional distillation of air? A methane B hydrogen C oxygen D sulfur dioxide ( C ) 3 Which of the following gases is not present in clean air? A oxygen B nitrogen C carbon dioxide D hydrogen ( D ) 4 Which of the following is not a source of sulfur dioxide? A combustion of coal B combustion of crude oil C lightning activity D volcanic eruption ( C )

2 5 Which of the following gases does not affect the pH of water? A carbon dioxide B carbon monoxide C nitrogen dioxide D sulfur dioxide ( B ) 6 Which of these chemicals can be used to test for the presence of sulfur dioxide in polluted air? A aqueous acidified potassium manganate(VII) B anhydrous copper(II) sulfate C aqueous hydrogen peroxide D limewater ( A ) 7 Which of the following about nitrogen dioxide is true? A It is a greenhouse gas. B It is produced when plant and animal matter decay. C It is released during complete combustion of petrol. D It causes acid rain. ( D ) 8 Which of the following is not a harmful effect of carbon monoxide? A It causes headaches. B It causes breathing difficulties. C It causes cancer. D It causes death. ( C ) 9 In the apparatus shown, 100 cm 3 of air are passed backwards and forwards between the two syringes until reaction is complete. On cooling to room temperature, what volume of gas remained? A 20 cm3 B 28 cm3 C 32 cm3 D 80 cm3 ( D ) 10 It was found that cars which were parked near a coal -fired power station often corroded more quickly. Which gas, when present in above average levels in the a ir, is a possible cause? A carbon dioxide B ozone C sulfur dioxide D water vapour ( C ) 11 Which atmospheric pollutants, emitted by internal combustion engines, are reacted together to convert them to less harmful products? A carbon monoxide and nitrogen dioxide B carbon monoxide and unburnt hydrocarbons C nitrogen dioxide and sulfur dioxide D sulfur dioxide and unburnt hydrocarbons ( A )

3 12 Fossil fuels are used to power some internal combustion engines. Which pollutants are produced by an internal combustion engine burning fossil fuels? 1 carbon monoxide 2 nitrogen oxides 3 sulfur dioxide A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only ( A ) 13 Which statements about the pollutant carbon monoxide are correct? 1 It is a colourless, odourless gas. 2 It is formed by incomplete combustion of natural gas. 3 It reacts with haemoglobin in the blood. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 ( D ) 14 Which gas is not produced when hydrocarbons are burnt in the internal combustion engine? A carbon dioxide B carbon monoxide C hydrogen D nitrogen oxides ( C ) 15 Which of the following substance is used in the removal of sulfur dioxide gas during flue gas desulfurisation? A calcium nitrate B calcium sulfate C calcium chloride D calcium carbonate ( D ) 16 The table gives the relative concentrations of polluting gases in the air in four different industrialised cities. In which city are limestone buildings most thr eatened by pollution? sulfur dioxide nitrogen dioxide ozone A 17 46 23 B 32 33 30 C 38 40 11 D 45 14 21 ( C ) 17 A sample of air was shaken with an alkaline solution of a compound called pyrogallol. The gases remaining did not support combustion. Which one of the following pairs of gases was removed from the air by the alkaline pyrogallol? A carbon dioxide and nitrogen B oxygen and carbon dioxide C oxygen and nitrogen D nitrogen and water vapour ( B ) 18 Why are catalytic converters fitted to car exhausts? A to decrease the amount of carbon dioxide emitted B to decrease the amount of nitrogen oxides emitted C to improve the energy conversion D to reduce global warming ( B )

4 19 Using manganese(IV) oxide as a catalyst, aqueous hydrogen peroxide decomposes to form oxygen. The diagram below shows how oxygen could be produced from the reaction and then collected. The first few test-tubes of collected gas should be rejected because the oxygen would be contaminated by A air B hydrogen C hydrogen peroxide D manganese(IV) oxide ( A ) 20 A 100 cm 3 sample of bottled gas used for diving was placed in a gas sy ringe in the apparatus shown. The gas was passed backward and forward over heated copper turni ngs. The results obtained were used to plot the graph. What is the percentage of oxygen in the bottled gas? A 20% B 30% C 70% D 80% ( B )

5 Structured Questions 21 A student wanted to find the percentage of oxygen in air. A wax candle was floated on water. The student lit the candle and lowered a gas jar over it, as seen in the following diagram. The candle flame slowly went out and the water level r ose in the jar. The student noted the final water level in the jar. (a) Explain why the candle flame go out. All the oxygen has been used up and combustion cannot occur without oxygen (b) Approximately how far up the gas jar did the water rise? 21 cm (c) Name two gases that are left in the gas jar after the candle goes out. carbon dioxide / argon / nitrogen 22 The table shows the composition of the atmosphere of the planet Mars. gas percentage composition carbon dioxide 95.3% nitrogen 1.7% argon 1.6% oxygen 0.2% other gases 1.2% How does the atmosphere on Mars differ from the atmosphere on Earth? The most abundant gas on Mars is carbon dioxide while that on Earth is nitrogen. The atmosphere on Mars is made up of 95.3% carbon dioxide, 1.7% nitrogen, 1.6% argon and 0.2% oxygen while that on Earth is respectively, 0.03%, 78%, 1% and 21%.

6 23 ‘Lean burn’ engines are a type of car engine. This table shows some information about lean burn engines compared to normal car engines. type of engine amount of air mixed with petrol operating temperature concentration of CO in exhaust gases concentration of nitrogen oxides in