CIE IGCSE Chemistry

Topic Questions

IGCSEChemistryCIETopic Questions10. Chemistry of the Environment10.2 Air Quality & Climate

10.2 Air Quality & Climate

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1a3 marks

The diagram shows some of the processes which determine the percentage of carbon dioxide in the atmosphere.

carbon-dioxide-in-the-atmosphere

Explain how combustion alters the percentage of carbon dioxide in the atmosphere.

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1b4 marks

Separate: Chemistry Only

Photosynthesis reduces the percentage of carbon dioxide in the atmosphere.

i)
Complete the word equation for photosynthesis.

carbon dioxide + water → ........................ + ........................ 

 [2]

ii)
State two essential conditions for the above reaction to occur.

[2]

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25 marks

Extended Only

The diagram shows part of the carbon cycle. This includes some of the processes which determine the percentage of carbon dioxide in the atmosphere.

 
part-carbon-cycle

i)
Carbon dioxide is one greenhouse gas. Name another one.

[1]
 
ii)
Explain why the combustion of waste crop material should not alter the percentage of carbon dioxide in the atmosphere.
[2]
iii)
In 1960 the percentage of carbon dioxide in the atmosphere was 0.032% and in 2008 it was 0.038%. Suggest an explanation for this increase.
[2]

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3a1 mark

Choose from the following list of gases. A gas may be chosen once, more than once or not at all.

sulfur dioxide hydrogen methane carbon monoxide
     
argon ethene butane

When burned in oxygen, the only product is water.

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3b1 mark

Extended Only

It can polymerise.

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3c1 mark

When reacted with oxygen, the only product is carbon dioxide.

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3d1 mark

It is produced by the decay of vegetation in the absence of oxygen.

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4a2 marks

Oxygen and nitrogen are the two main gases in unpolluted air. 

State the percentage of each gas.


Gas  % in unpolluted air
nitrogen  
oxygen  

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4b2 marks

Extended Only

Greenhouse gases can be released into the atmosphere. 

Name two greenhouse gases.

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4c2 marks

Extended Only

Increasing amounts of greenhouse gases lead to global climate change. 

Give two effects of global warming.

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4d2 marks

Which strategies will reduce the effects of climate change?


Tick (✓) two boxes.

 
 Use of catalytic converters  
 Planting trees  
 Deforestation  
 Reduced livestock farming  
 Increased use of landfill  

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5a1 mark

The following can all be found in air. 

For each question choose a gas. A gas may be chosen once, more than once or not at all.

carbon monoxide sulfur dioxide carbon dioxide nitrogen
     
oxides of nitrogen particulates argon

Which gas is toxic and formed from incomplete combustion of methane?

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5b1 mark

Extended Only

Which gas is formed in cars and removed using catalytic converters?

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5c1 mark

Which substance increases the risk of cancer?

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5d1 mark

Which two gases cause acid rain?

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1a2 marks

Clean dry air contains mainly nitrogen and oxygen.

Name two other gases that are in clean dry air.

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1b6 marks

Air often contains pollutants.

Identify three common gaseous pollutants in air and state how each of these pollutants are produced.

pollutant gas 1 ..................................................
how it is produced ..................................................

pollutant gas 2 ..................................................
how it is produced ..................................................

pollutant gas 3 ..................................................
how it is produced ..................................................

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2a2 marks

Air is a mixture of gases.

The main constituents are the elements oxygen and nitrogen.

i)
Name another element in air.

[1]

 

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

[1]

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2b6 marks

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

i)
How are the oxides of nitrogen formed?
[2]
ii)
How is sulfur dioxide formed?
[2]
iii)
These oxides are largely responsible for acid rain.
State two harmful effects of acid rain.
[2]

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2c5 marks

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

calculating-the-percentage-of-air
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.

[2]

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

[1]

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

[1]

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

[1]


.

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3a7 marks

Plant growth is improved by the availability of essential elements, such as nitrogen, and by the soil having a suitable pH.

Nitrogen-based fertilisers are made from ammonia. Ammonia is manufactured by the Haber process.

i)
Describe the Haber process giving reaction conditions and a balanced equation.
(Do not discuss reaction rate and yield.)

[5]
ii)
Fertilisers contain nitrogen.
Name the other two elements essential for plant growth commonly found in fertilisers.
[2]

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3b5 marks

Crops do not grow well if the soil is too acidic.

i)
One cause of acidity in soil is acid rain. Explain how acid rain is formed.

[3]

ii)
Name two bases which are used to increase the pH of acidic soils.

[2]

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4a8 marks

Polluted air contains two oxides of carbon and two oxides of nitrogen. A major source of these pollutants is motor vehicles.

i)
Describe how carbon dioxide and carbon monoxide are formed in motor vehicle engines.

[3]

 

ii)
State one adverse effect of each of these gases.

[2]

iii)
Nitrogen monoxide, NO, is released by motor vehicle exhausts.

Explain how nitrogen monoxide is formed in motor vehicle engines.

[2]

iv)
When nitrogen monoxide is released into the atmosphere, nitrogen dioxide, NO2, is formed.
Suggest an explanation why this happens.

[1]

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4b2 marks

Predict the possible adverse effect on the environment when this non-metal oxide, NO2, reacts with water and oxygen.

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4c3 marks

How are the amounts of carbon monoxide and nitrogen monoxide emitted by modern motor vehicles reduced?

Include an equation in your answer.

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5a2 marks

Three common pollutants in the air are carbon monoxide, the oxides of nitrogen, NO and NO2 and unburnt hydrocarbons. They are all emitted by motor vehicles.

Describe how the oxides of nitrogen are formed.

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5b4 marks

Describe how a catalytic converter reduces the emission of these three pollutants.

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6a3 marks
i) 
Coal is a solid fossil fuel. Name another fossil fuel.

[1]

ii)
Explain what is meant by the term fossil fuel.
[2]

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6b10 marks

The burning of fossil fuels is largely responsible for the formation of acid rain. Two of the acids in acid rain are sulfuric acid and nitric acid.

i)
Explain how the combustion of coal can form sulfuric acid.

[3]

ii)
High temperatures generated by the combustion of fossil fuels can lead to the formation of nitric acid. Explain.

[3]

iii)
Nitric acid contains nitrate ions.
Describe a test for nitrate ions.

[2]

iv)
Explain how you could determine which one of two samples of acid rain had the higher concentration of hydrogen ions.

[2]

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19 marks

Separate: Chemistry and Extended Only

Ozone is a form of oxygen. Ozone is present in the upper atmosphere and it prevents dangerous solar radiation from reaching the Earth’s surface. Some of the chemicals that diffuse into the upper atmosphere decompose ozone. Chemicals that have this effect are methane (CH4), chloromethane (CH3Cl) and an oxide of nitrogen (NO2).

i)
Which of these three chemicals diffuses the most slowly? Give a reason for your choice.
[2]
ii)
Chloromethane is formed when seaweed decomposes. Name the compounds in the environment from which seaweed might have obtained the following elements:

carbon; .................................................................................................................
hydrogen; ............................................................................................................
chlorine. ................................................................................................................ 

[3]

iii)
How can chloromethane be made from methane?

reagent .................................................................................................................
condition ...............................................................................................................

[2]

iv)
The oxides of nitrogen are atmospheric pollutants. Describe how they are formed.
[2]

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2a3 marks

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

i)
Name another gaseous element in unpolluted air.
[1]

ii)
Name two compounds in unpolluted air.
[2]

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2b7 marks

Extended Only

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

i)
Name another pollutant in air.
[1]

ii)
Describe how carbon monoxide is formed.
[2]
iii)
How are the oxides of nitrogen formed?
[2]

iv)
Explain how a catalytic converter reduces the emission of these two gases.
[2]

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3a5 marks

This question is concerned with the following oxides.

sulfur dioxide
carbon monoxide
lithium oxide
aluminium oxide
nitrogen dioxide
strontium oxide

Two of the oxides are responsible for acid rain.


Identify the two oxides and explain their presence in the atmosphere.

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3b3 marks

Lithium oxide is an ionic compound.

i)
Identify another ionic oxide in the list in part a).

[1]
ii)
Draw a diagram which shows the formula of lithium oxide, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from an atom of oxygen.
Use o to represent an electron from an atom of lithium.
[2]

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4a4 marks

Extended Only

When nitrogen dioxide is cooled, it forms a yellow liquid and then pale yellow crystals. These crystals are heated and the temperature is measured every minute. The following graph can be drawn.

 
time-temp-no2
 
i)
Describe the arrangement and movement of the molecules in the region A–B.
 
ii)
Name the change that occurs in the region B–C

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4b4 marks

Extended Only

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

 
i)
Explain how these oxides are formed.
 
ii)
How are they removed from the exhaust gases?

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4c3 marks

Nitrogen dioxide, oxygen and water react to form dilute nitric acid.

Describe how lead(II) nitrate crystals could be prepared from dilute nitric acid and lead(II) oxide.

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5a2 marks

Separate: Chemistry and Extended Only

The reactions in this question are all examples of photochemical reactions.

Explain the phrase photochemical reaction.

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5b6 marks

Separate: Chemistry Only

Many millions of years ago, the Earth’s atmosphere was rich in carbon dioxide and contained negligible amounts of oxygen. After the appearance of green plant-like bacteria, the proportions of these two gases in the atmosphere changed.

i)
What are the approximate percentages of these two gases in the atmosphere now?
 
carbon dioxide = ..................................................
 
oxygen = .................................................. 
[2]

ii)
Explain how the green plant-like bacteria changed the composition of the atmosphere.
[4]

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6a4 marks

Minimising air pollution is essential for health and for the environment.

Natural gas is methane.

i)
Write the equation for complete combustion of methane.
[2]

ii)
Explain why it is dangerous to use a gas fire in a poorly ventilated room.
[2]

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6b2 marks

Low sulfur fuels are being introduced. Ordinary diesel contains 500 ppm of sulfur but low sulfur diesel contains less than 50 ppm. Why is this an advantage to the environment?

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6c3 marks

Extended Only

Catalytic converters reduce pollution from motor vehicles, as shown in the following diagram.

catalytic-converters

i)
What type of elements are the metals rhodium, platinum and palladium?
[1]
ii)
Rhodium catalyses the decomposition of the oxides of nitrogen.

2NO → N2 + O2

Two other pollutants are carbon monoxide and unburnt hydrocarbons. How are they made into less harmful substances?
[2]

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7a2 marks

Coal is a solid fossil fuel.

Name two other fossil fuels.

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7b2 marks

Two of the elements present in a sample of coal are carbon and sulfur. 


A sample of coal was heated in the absence of air and the products included water, ammonia and hydrocarbons.

Name three other elements present in this sample of coal.

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7c5 marks

Sulfur, present in coal, is one major cause of acid rain. Sulfur burns to form sulfur dioxide which reacts with rain water to form sulfuric acid.

i)
Describe how the high temperatures in vehicle engines are another cause of acid rain.
[3]
ii)
Give two harmful effects of acid rain.
[2]

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7d3 marks

In 2010, a large coal-burning power station in the UK was converted to burn both coal and wood.

Explain why the combustion of wood rather than coal can reduce the effect of the emissions from this power station on the level of carbon dioxide in the atmosphere.

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8a1 mark

The properties of five alkenes at room temperature are shown in the table.

alkene number of carbon atoms in a molecule state at room temperature density
in g / cm3		 boiling point / °C
ethene 2 gas 0.0012 –104
propene 3 gas 0.0018 –47
butene 4 gas 0.0024  
pentene 5 liquid 0.64 30
hexene 6 liquid 0.67 63

When propene undergoes incomplete combustion, carbon monoxide is formed.

What condition is needed for incomplete combustion?

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8b1 mark

Give one adverse effect of carbon monoxide on health.

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