O LevelChemistryCambridgeTopic Questions10. Chemistry of the Environment10.1 Water & Water Pollution

Water & Water Pollution (Cambridge O Level Chemistry)

Topic Questions

DownloadView
Easy
Medium
Hard
Easy
Medium
Hard
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. 

How did you do?

1b4 marks

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

How did you do?

1c2 marks

Explain why tap water is not used for chemical reactions.

How did you do?

Did this page help you?

2a2 marks

This question is about water:

State two industrial uses of water.

How did you do?

2b2 marks

State two uses of water in the home.

How did you do?

2c2 marks

Before water is used in industrial processes and in the home it must be purified. Give two substances which are found in natural water before purification.

How did you do?

2d1 mark

State the term that describes a rock that store water.

How did you do?

Did this page help you?

3a1 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   

How did you do?

3b1 mark

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

How did you do?

3c2 marks

Untreated water contains soluble and insoluble impurities. 

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

How did you do?

3d1 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 ........................

How did you do?

Did this page help you?

4a1 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.

How did you do?

4b1 mark

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

How did you do?

4c1 mark

Suggest another use for which chlorinated water is required.

How did you do?

4d1 mark

Describe what happens in the sedimentation tank.

How did you do?

Did this page help you?

1a3 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.

How did you do?

1b2 marks

Explain why it is beneficial to drink water that is not deionized.

How did you do?

1c1 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.

How did you do?

1d3 marks

When chlorine is added to water it undergoes a reaction which forms hydrogen chloride and chloric(I) acid. The chloric(I) acid is the compound that kills the bacteria. 

Cl2 + H2O → HCl + HClO

In this reaction chlorine is both oxidised and reduced. Explain why.

How did you do?

Did this page help you?

2a6 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.

How did you do?

2b2 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]

How did you do?

2c
Sme Calculator3 marks

A common test for water is to use anhydrous copper(II) sulfate. If water is present an exothermic reaction takes place and the solid turns from white to blue and becomes hydrated copper(II) sulfate. This reaction is reversible.

6.25 g of blue hydrated copper(II) sulphate, CuSO4.xH2O was gently heated in a crucible until the mass remaining was 4.00 g. This is the white anhydrous copper(II) sulphate. 

Use this information to calculate a value for x in CuSO4.xH2O.  

Ar's Cu = 64, S = 32, O = 16, H = 1 

x = ..............

How did you do?

2d3 marks

Cobalt(II) chloride paper is used to test for water as well. Hydrated cobalt chloride has the formula CoCl2∙6H2O.

 
i)
State the colour change when cobalt chloride paper is added to water.
 
[1]
 
ii)
When hydrated cobalt chloride is heated, water is given off. Write the balanced symbol equation for this reaction. 
 
[2]

How did you do?

Did this page help you?

1a3 marks

This question is about water.

Describe a chemical test which shows the presence of water.


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

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

How did you do?

1b1 mark

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

How did you do?

1c2 marks

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

How did you do?

Did this page help you?

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]

How did you do?

2b2 marks

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

How did you do?

Did this page help you?

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]

How did you do?

3b2 marks

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

How did you do?

3c6 marks
i)
Explain how acid rain is formed.
 
[4]
 
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.
 
[2]

How did you do?

Did this page help you?

4a2 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.

How did you do?

4b3 marks

Explain why chlorination is required.

How did you do?

4c
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.

How did you do?

4d3 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.

How did you do?

Did this page help you?