12_Air and Water

Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

220

Topic 12

Composition of air

Air pollution

Reduction of air pollution

Purification of water supply

Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

221

1) Nov 2001 Q (1_a, i, ii)

1 a) The poisonous gas, carbon monoxide, is emitted by vehicle exhausts.

(i) How is this gas formed?

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(ii) Explain how a catalytic converter reduces the emission of this gas.

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2) Nov 2001 Q (2_a, i, ii)

a)

(i) Describe how oxygen is separated from air.

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(ii) Give one use of oxygen

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3) June 2002 Q (3_b, c)

b) One of the reasons for using hydrogen as a fuel is to reduce air pollution. Petroleum powered vehicles are a major cause of air pollution. This pollution can be decreased by reactions of the type shown below.

2 22 2 2CO NO N CO

(i) Where in a vehicle does this type of reaction occur?

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(ii) Explain how carbon monoxide is formed in the engine.

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(iii) Give a reason why the hydrogen-powered vehicle produces less pollution.

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c) Outline how hydrogen is manufactured from water.

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Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

222

4) June 2003 Q (4_c)

c) Nitrogen dioxide and other oxides of nitrogen are formed in car engines.

(i) Explain how these oxides are formed.

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(ii) How are they removed from the exhaust gases?

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5) Nov 2004 Q (1_a, b)

a) Two of the gases in air are nitrogen and oxygen. Name two other gases present in unpolluted air. …………………………………………………………………………………………

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b) Two common pollutants present in air are sulfur dioxide and lead compounds. State the source and harmful effect of each.

sulfur dioxide

Source ……………………………………………………………………….

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Harmful effect …………………………………….………………………………[3]

lead compounds

Source ……………………………………………………………………….

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6) Nov 2009 Q (1_a, b)

a) The major gases in unpolluted air are 79% nitrogen and 20% oxygen

(i) Name another gaseous element in unpolluted air

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(ii) Name two compounds in unpolluted air …………………………………………………………………………………………

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Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

223

b) Two common pollutants in air are carbon monoxide and the oxides of nitrogen

(i) Name another pollutant in air

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(ii) Describe how carbon monoxide is formed …………………………………………………………………………………………

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(iii) How are the oxides of nitrogen formed? …………………………………………………………………………………………

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(iv) Explain how a catalyst converter reduces the emission of these gases …………………………………………………………………………………………

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7) June 2010 Q (2_iv)

(iv) The oxides of nitrogen are atmospheric pollutants. Describe how they are formed.

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8) Nov 2011 [32] Q (7_d)

(d) Some of the pollutants emitted by vehicle exhausts are carbon monoxide, oxides of nitrogen and unburnt hydrocarbons. Explain how the emission of these gases is reduced by a catalytic converter.

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Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

224

9) June 2012 [31] Q (1_b, c)

1) The diagram below shows part of the Water Cycle.

(b) The rain drains into rivers and then into reservoirs. Describe how water is treated before it enters the water supply.

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(c) (i) Explain how acid rain is formed.

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(ii) Fish live in water which is neutral (neither acidic nor alkaline). Acid rain decreases the pH of water in lakes and rivers. Both of the bases, calcium oxide and calcium carbonate, can neutralise this acid and increase the pH. Explain why calcium carbonate is a better choice.

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10) Nov 2012 [31] Q (3_c)

(c) Catalytic converters reduce the pollution from motor vehicles.

Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

225

(i) Describe how carbon monoxide and the oxides of nitrogen are formed in car engines.

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(ii) Describe the reaction(s) inside the catalytic converter which change these pollutants into less harmful gases. Include at least one equation in your description.

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11) June 2013 [32] Q (1)

1 Air is a mixture of gases. The main constituents are the elements oxygen and nitrogen.

(a) (i) Name another element in air.

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(ii) Give the formula of a compound in unpolluted air.

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(b) Common pollutants present in air are the oxides of nitrogen and sulfur dioxide.

(i) How are the oxides of nitrogen formed?

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(ii) How is sulfur dioxide formed?

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(iii) These oxides are largely responsible for acid rain.

State two harmful effects of acid rain.

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Classified Chemistry IGCSE Paper_3_Topic 12

12 Air and Water Mostafa Barakat (0100 165 44 62)

226

(c) The percentage of oxygen in air can be determined by the following experiment.

The gas syringe contains 50 cm3 of air. The large pile of copper is heated and the air is passed from one gas syringe to the other over the hot copper. The large pile of copper turns black. The gas is allowed to cool and its volume measured.

The small pile of copper is heated and the remaining gas passed over the hot copper.

The copper does not turn black. The final volume of gas left in the apparatus is less than 50 cm3.

(i) Explain why the copper in the large pile turns black.

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(ii) Why must the gas be allowed to cool before its volume is measured?

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(iii) Explain why the copper in the small pile did not turn black.

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(iv) What is the approximate volume of the gas left in the apparatus?

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