IGCSEChemistry: Co-ordinated Sciences (Double Award)CIEExam QuestionsChemistry of the EnvironmentWater & Water Pollution

Water & Water Pollution (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

Exam Questions

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1a4 marks

This question is about chemical tests for water.

Complete these sentences about the test for water using the words from the list.

hydrated  green  anhydrous white
blue sulfur yellow sulfate


Cobalt chloride paper will turn from .......................... to pink in the presence of water.

.............................. copper ........................ will turn from ........................... to blue in the presence of water. 

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1b4 marks

Describe how a student could test to see if a sample of water is pure.

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1c2 marks

Explain why tap water is not used for chemical reactions.

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2a1 mark

This question is about the testing and purification of water

Which of these statements describes the correct test for water?
Tick one box.

Hydrated copper(II) sulfate stays white  
   
Hydrate copper(II) sulfate turns pink  
   
Cobalt chloride paper turns pink   
   
Cobalt chloride paper turns white   

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2b1 mark

When water is added to hydrated copper(II) sulfate heat is produced. What type of reaction is this?

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2c2 marks

Untreated water contains soluble and insoluble impurities. 

Name the two processes that remove insoluble impurities during the treatment of water.

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2d1 mark

Complete the following sentence using the words from the list

 
chlorine carbon sand
 

In order to remove odours and tastes water is passed through ........................

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3a1 mark

The flow chart shows stages in producing drinking water.

bold reservoir bold rightwards arrow bold sedimentation bold space bold tank bold rightwards arrow bold filtration bold space bold tank bold space bold rightwards arrow bold space bold antibacterial bold space bold treatment bold space bold tank bold rightwards arrow bold storage bold space bold tank bold rightwards arrow bold mains

At which stage is chlorine added to the water.

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3b1 mark

Chlorine is a toxic substance. Suggest why it is safe to be added to drinking water.

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3c1 mark

Suggest another use for which chlorinated water is required.

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3d1 mark

Describe what happens in the sedimentation tank.

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1a3 marks

This question is about water.

Describe a chemical test which shows the presence of water.


test ..................................................

colour change if water is present  ..................................................

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1b1 mark

How could you show that a sample of water is pure?

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1c2 marks

Describe how water is treated before it is supplied to homes and industry.

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2a4 marks

Water is needed for industry and in the home.

i)
Rain water is collected in reservoirs. How is it treated before entering the water supply?
 
[2]
 
ii)
State two uses of water in the home.
 
[2]

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2b2 marks

In many regions, drinking water is obtained by the distillation of sea-water. Explain how distillation separates the water from sea-water.

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3a3 marks

The diagram below shows part of the Water Cycle.

screen-shot-2023-02-22-at-11-18-34

i)
State the name of each of the following changes of state.
 
H2O (l) → H2O (g)
 
name ..................................................
 
H2O (g) → H2O (l)
 
name ..................................................
 
[2]
 
ii)
Which one of the above changes of state is exothermic? Explain your choice.
 
[1]

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3b2 marks

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

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41 mark

Calcium nitrate is used as a fertiliser to help prevent blossom end rot in tomatoes which causes browning of the bottom of the fruit. It provides both calcium and nitrogen.

Write the formula for calcium nitrate.

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5a2 marks

Waste water like this needs to be treated before being released into the environment. Waste water may require removal of organic matter and harmful chemicals. The three main steps are sedimentation, filtration and chlorination.

Explain what happens in sedimntation.

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5b3 marks

Explain why chlorination is required.

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5c
Sme Calculator3 marks

Table 5.1 shows some information about how the treated solid sludge was disposed of from one sewage treatment plant in 2000 and 2020.

Table 5.1

Mass of treated solid sludge in tonnes
Year Used as fertiliser Sent to landfill Other Total
2000 56 22 55 132
2020 152 2 39 193

Calculate the percentage of treated solid sludge that was sent to landfill in 2000.

Give your answer to 3 significant figures.

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5d3 marks

The total mass of treated solid sludge increased from 2000 to 2020 and the proportions of how the sludge was disposed of changed.

Suggest one reason for the increase in the total mass of treated solid sludge and two reasons for the changes in the proportions of the disposal methods.

Use Table 5.1 to help you answer.

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13 marks

Fertilisers are used to promote plant growth.

Two fertilisers are ammonium phosphate, (NH4)3PO4, and calcium dihydrogenphosphate,Ca(H2PO4)2.

Describe a test to distinguish between these two fertilisers.

test ..................................................

result ..................................................

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2
Sme Calculator5 marks

Higher tier only

The equation for the decomposition of copper(II) nitrate is given below.

2Cu(NO3)2 → 2CuO + 4NO2 + O2

Copper(II) nitrate forms a series of hydrates with the formula Cu(NO3)2.xH2O.

All these hydrates decompose to form copper(II) oxide.

1 mole of Cu(NO3)2.xH2O forms 1 mole of CuO.
 

i)
What is meant by 1 mole of a substance?
 
[1]
 
ii)
7.26 g of a hydrate, Cu(NO3)2.xH2O, formed 2.4 g copper(II) oxide.

number of moles of CuO formed = ......................
number of moles of Cu(NO3)2.xH2O in 7.26 g = ......................
mass of 1 mole of Cu(NO3)2.xH2O = ...................... g
mass of 1 mole of Cu(NO3)2 is 188 g
the value of x in this hydrate = ......................
 
[4]

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34 marks

Groundwater can contain fertilisers washed from fields. An example of a fertiliser that can be found is ammonium nitrate. 

i)
Write a balanced equation, including state symbols, to show how ammonium nitrate can be made by a student via a neutralisation reaction. 
 
[2]
 
ii)
Describe how the student could perform a chemical test for the presence of nitrate ions.
 
[2]

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4a3 marks

Water from reservoirs is treated to make it suitable for drinking. Even though the water has been treated it is not pure. One method to purify water is de-ionisation.

Describe another method which will produce pure water.

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4b1 mark

Chlorine is added to drinking water in order to make it safe to drink. The chlorine kills miro-organisms that can cause illnesses such as cholera and typhoid.

Suggest a concern with adding chlorine to drinking water.

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5a6 marks

A scientist finds an unlabelled bottle on a shelf.

She thinks the bottle contains a solution of ammonium sulfate, (NH4)2SO4.

Describe tests the scientist could do to show that the solution is ammonium sulfate.

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5b2 marks

Ammonium sulfate is often used as a fertiliser.

It is prepared by reacting ammonia (NH3) with sulfuric acid (H2SO4).

 
i)
Name the type of reaction that occurs between ammonia and sulfuric acid.
 
[1]
 
ii)
Write a chemical equation for the reaction of ammonia with sulfuric acid.
 
[1]

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