CIE IGCSE Chemistry

Topic Questions

IGCSEChemistryCIETopic Questions12. Experimental Techniques & Chemical Analysis12.2 Separation & Purification

12.2 Separation & Purification

DownloadView
Easy
Medium
Hard
Easy
Medium
Hard
1a1 mark

A list of techniques used to separate mixtures is given below.

  • fractional distillation
  • simple distillation
  • crystallisation
  • filtration
  • diffusion

From the list choose the most suitable technique to separate the following:

water from aqueous copper(II) sulfate.............................

How did you do?

1b1 mark

Helium from a mixture of helium and argon.......................

How did you do?

1c1 mark

Copper(II) sulfate from aqueous copper(II) sulfate.

How did you do?

1d1 mark

Ethanol from aqueous ethanol.

How did you do?

1e1 mark

Barium sulfate from a mixture of water and barium sulfate.

How did you do?

Did this page help you?

2a1 mark

Alcohols can be partially oxidised to form aldehydes. Aldehydes are a homologous series of organic compounds.

Partial oxidation is achieved by reacting an alcohol with the oxidising agent in the apparatus as shown.

q5c_0620-s20-qp-41_cie-igcse-chemistry

Give the name of this process that is used to separate a mixture of liquids with different boiling points.

How did you do?

2b1 mark

Name apparatus A.

How did you do?

2c1 mark

On the diagram, use one arrow to show where water enters apparatus A.

How did you do?

Did this page help you?

3a1 mark

Chromatography can be used to test the purity of substances.

The diagram shows the chromatogram of a coloured substance.

q4c0620-s20-qp-43

How does this chromatogram show that this substance is not pure?

How did you do?

3b1 mark

Extended Only

Draw a circle around the correct Rf value for the spot labelled X.

 
0.2      0.4     0.8      1.2

How did you do?

3c1 mark

Separate: Chemistry and Extended Only

State how a colourless substance can be made visible on a chromatogram.

How did you do?

Did this page help you?

4a4 marks

Substances can be classified as elements, compounds or mixtures.

Each of the boxes in the diagram represents either an element, a compound or a mixture.

2-2-methods-of-separating-and-purifying-substances
i)
Explain which two boxes represent an element.
 (2)
ii)
Explain which two boxes represent a mixture.
(2)

How did you do?

4b3 marks

The list gives the names of some methods used in the separation of mixtures:

  • chromatography
  • crystallisation
  • distillation
  • filtration

Use names from the list to choose a suitable method for each separation. Each name may be used once, more than once or not at all.

i)
Separating water from sodium chloride solution.
(1) 
iii)
Separating the blue dye from a mixture of blue and red dyes.
(1) 
iii)
Separating potassium nitrate from potassium nitrate solution.
(1) 

How did you do?

4c2 marks

The colours in three different dyes, A, B & C, were investigated using paper chromatography.

The dyes are soluble in propanone but not soluble in water.

The apparatus used is shown.

aqa-gcse-8-1e-tq3b-chromatography-equipment
 

Place two ticks in boxes that identify how the equipment was incorrectly set up. 

The dyes are all on the same piece of chromatography paper  
The solvent used is water  
A lid is on the beaker  
The water is not level with the dyes  
The start line is drawn in ink  

How did you do?

4d3 marks

The student corrected the mistakes and obtained the chromatogram shown in Figure 2.

aqa-gcse-8-1e-tq3c-chromatogram-of-dyes
Figure 2 



Put ticks (✔ ) in the boxes to show which statements are true and which statements are false. 

  True False
 Dye A is the most soluble     
 Dye C is a mixture    
 Dye C contains dye B     
 Dye C contains dye A    
 Dye B is a pure substance    

How did you do?

Did this page help you?

5a1 mark

Rock salt is a mixture of sand and salt. Salt dissolves in water. Sand does not dissolve in water.

A student sepearted a sample of rock salt using this method:

  1. Place the rock salt in a beaker.
  2. Add 100 cm3 of cold water.
  3. Allow the sand to settle to the bottom of the beaker.
  4. Carefully pour the salty water into an evaporating dish.
  5. Heat the contents of the evaporating dish with a Bunsen burner until salt crystals start to form.

Suggest one improvement to step 2 to make sure all the salt is dissolved in the water.

How did you do?

5b1 mark

Step 3 produces the salty water which is used in step 4. This salty water contains very small grains of sand.

Suggest one improvement to step 4 to remove all the sand.

How did you do?

5c2 marks

Another student distilled the water from the salty water using the apparatus shown.

 
12-2-5c-e-saltwater-distillation
 

State the name of the processes occurring at A and B.

How did you do?

5d1 mark

What is the reading on the thermometer during this distillation?

How did you do?

Did this page help you?

1a
Sme Calculator2 marks

In 1985 the fullerenes were discovered. They are solid forms of the element carbon. The structure of the C60 fullerene is given below.

wGYbHIxu_fullerene

i)
In the C60 fullerene, how many other carbon atoms is each carbon atom bonded to?
[1]

ii)
Another fullerene has a relative molecular mass of 840.
How many carbon atoms are there in one molecule of this fullerene?
[1]

How did you do?

1b3 marks

Fullerenes are soluble in liquid hydrocarbons such as octane. The other solid forms of carbon are insoluble.

Describe how you could obtain crystals of fullerenes from soot which is a mixture of fullerenes and other solid forms of carbon.

How did you do?

1c5 marks

A mixture of a fullerene and potassium is an excellent conductor of electricity.

i)
Which other form of solid carbon is a good conductor of electricity?
[1]

ii)
Explain why metals, such as potassium, are good conductors of electricity.
[2]

iii)
The mixture of fullerene and potassium has to be stored out of contact with air. There are substances in unpolluted air which will react with potassium.
Name two potassium compounds which could be formed when potassium is exposed to air.
[2]

How did you do?

Did this page help you?

2a2 marks

The ester linkage showing all the bonds is drawn as

ester-linkage

or more simply it can be written as –COO–.

i)
Give the structural formula of the ester ethyl ethanoate.

[1]

ii)
Deduce the name of the ester formed from methanoic acid and butanol.

[1]

How did you do?

2b3 marks

Draw the structural formula of the polyester formed from the following monomers.

 
HOOCC6H4COOH and HOCH2CH2OH
 

You are advised to use the simpler form of the ester linkage.

How did you do?

2c5 marks

Esters can be used as solvents in chromatography. The following shows a chromatogram of plant acids.

chromatogram-of-plant-acid

An ester was used as the solvent and the chromatogram was sprayed with bromothymol blue.

i)
Suggest why it was necessary to spray the chromatogram.

[2]

ii)
Explain what is meant by the Rf value of a sample.

[1]

iii)
Calculate the Rf values of the two samples and use the data in the table to identify the plant acids.

Plant acid Rf value
tartaric acid 0.22
citric acid 0.30
oxalic acid 0.36
malic acid 0.46
succinic acid 0.60

[2]

How did you do?

Did this page help you?

3a2 marks

A student is told to produce the maximum amount of copper from a mixture of copper and copper(II) carbonate.

The student adds the mixture to an excess of dilute sulfuric acid in a beaker and stirs the mixture with a glass rod. The copper(II) carbonate reacts with the sulfuric acid, forming a solution of copper(II) sulfate but the copper does not react with the sulfuric acid.

The student then

  • removes the unreacted copper from the mixture,
  • converts the solution of copper(II) sulfate into copper by a series of reactions.

Describe two things that the student would observe when the mixture is added to the dilute sulfuric acid.

How did you do?

3b3 marks

Describe how the student can produce pure dry copper from the mixture of copper and copper(II) sulfate solution.

How did you do?

3c2 marks

The student then adds sodium hydroxide solution to the copper(II) sulfate solution to produce copper(II) hydroxide. 

i)
Describe what the student would observe.

[1]

ii)
Write an ionic equation for this reaction.

[1]

How did you do?

3d3 marks

After separating the copper(II) hydroxide from the mixture, the copper(II) hydroxide is heated strongly. The copper(II) hydroxide decomposes into copper(II) oxide and steam.

i)
Write an equation for the decomposition of copper(II) hydroxide. Include state symbols.

[2]

ii)
Name a non-metallic element that can be used to convert copper(II) oxide into copper.

[1]

How did you do?

Did this page help you?

4a4 marks

Extended Only

Electrolysis is used to manufacture magnesium from molten magnesium bromide.

 
i)
The negative electrode is made of iron.
 
Suggest a non-metal which could be used for the positive electrode.
Give a reason for your answer.
 
[2]
 
ii)
Write the ionic equations for the products of the electrolysis of molten magnesium bromide at:
 
the positive electrode ..........................................................................................................
 
the negative electrode. .......................................................................................................
 
[2]

How did you do?

4b2 marks

The following statements are about the procedure for making crystals of hydrated magnesium bromide from magnesium and dilute hydrobromic acid.

A

Add an excess of magnesium to dilute hydrobromic acid.
B

Filter off the crystals and dry between filter papers.
C

Filter off the excess magnesium.
D

Leave the mixture at room temperature to form more crystals.
E

Leave the mixture until no more bubbles are seen.
F

Warm the filtrate to the point of crystallisation.

Put the statements A, B, C, D, E and F in the correct order.

How did you do?

4c2 marks

Magnesium is a metal in Group II of the Periodic Table.

Cobalt is a transition element with a higher melting point and a higher boiling point than magnesium.

Describe two other properties of cobalt which are different from those of magnesium. 

How did you do?

4d4 marks

Chromatography can be used to separate a mixture of ions from different transition element compounds.

Two solutions, Y and Z, each containing only one type of transition element ion were placed on a piece of chromatography paper.

Four samples, R, S, T and U, each containing transition element ions, were also placed on the same piece of chromatography paper.

 

The results of the chromatography are shown.

12-2-4d-h-chromatography-results 
i)
Explain the results shown for solutions Y and Z.
 
[1]
 
ii)
Which sample, R, S, T or U, does not contain the same ions as either solution Y or solution Z?
 
[1]
 
iii)
Which sample, R, S, T or U, contains the same ions as both solution Y and solution Z?
 
[1]
 
iv)
Which sample, R, S, T or U, has the greatest number of transition element ions?
 
[1]

How did you do?

Did this page help you?

5a3 marks

An ink is a mixture of coloured substances dissolved in water.

A sample of ink, K, is known to contain three different coloured substances.

Evaluate the use of the following methods to separate the coloured substances in the sample of ink, K.

 
  • chromatography
  • crystalisation
  • filtration
  • fractional distillation
  • simple distillation
 

How did you do?

5b3 marks

The apparatus shown can be used to separate water from ink.

 
fig-9-q6b-1cho-1f-paper-1-june-2018
 
i)
Cold water flows through the condenser. 
 
Add labelled arrows to the diagram to show where the water should flow in and out of the apparatus
 
[1]
 
ii)
Explain why a condenser is used.
 
[1]
 
iii)
The flask was heated with a Bunsen burner.
 
Name an alternative piece of apparatus that could be used to heat the flask.
 
[1]

How did you do?

5c2 marks

The arrangement of the particles in the ink inside the flask is shown.

 
fig-10-q6c-1cho-1f-paper-1-june-2018
 

In the boxes below, draw the arrangement of particles that would be expected at A and B shown in part (b).

fig-q6c-1cho-1f-paper-1-june-2018

How did you do?

Did this page help you?

1a3 marks

Describe how to separate the following. In each example, give a description of the procedure used and explain why this method works.

Copper powder from a mixture containing copper and zinc powders.

procedure..............................................

explanation .........................................

How did you do?

1b3 marks

Nitrogen from a mixture of nitrogen and oxygen.

procedure............................................

explanation........................................

How did you do?

1c2 marks

Glycine from a mixture of the two amino acids glycine and alanine. Glycine has the lower Rf value.

procedure.........................................

explanation.....................................

How did you do?

1d3 marks

Magnesium hydroxide from a mixture of magnesium hydroxide and zinc hydroxide.

procedure..................................................

explanation..............................................

How did you do?

Did this page help you?

2a1 mark

An important aspect of chemistry is purity and methods of purification.

Give an example of a substance used in everyday life which must be pure.

How did you do?

2b9 marks

A list of techniques used to separate mixtures is given below.

 
chromatography crystallisation  diffusion
evaporation filtration fractional distillation simple distillation
 
i)
From the list, choose the most suitable technique to separate the following.
 
Water from sea-water ........................................................................
 
Helium from a mixture of helium and methane .................................
 
Ethanol from a mixture of ethanol and propanol ...............................
 
Iron filings from a mixture of iron filings and water ..........................
 
A mixture of two amino acids, glycine and alanine ...........................

[5]

ii)
Describe how you would obtain a pure sample of copper(II) sulfate-5-water crystals from a mixture of copper(II) sulfate-5-water with copper(II) oxide using some of the techniques listed above.
[4]

How did you do?

Did this page help you?

3a2 marks

Petroleum contains hydrocarbons which are separated by fractional distillation.

i)
Complete the following definition of a hydrocarbon:

A hydrocarbon is a compound which ............................................
[1]
ii)
Explain what is meant by the term fractional distillation.
[1]

How did you do?

3b4 marks

Some of the fractions obtained from petroleum are given below. State a use for each fraction.

bitumen ....................................................................


lubricating fraction ..............................................


paraffin fraction ........................................................


gasoline fraction ......................................................

How did you do?

Did this page help you?

4a1 mark

A list of techniques used to separate mixtures is given below.

filtration
diffusion
fractional distillation
simple distillation
crystallisation
chromatography

From this list, choose the most suitable technique to separate the following mixtures.

 A technique may be used once, more than once or not at all.

Butane from a mixture of propane and butane.

How did you do?

4b1 mark

Oxygen from liquid air.

How did you do?

4c1 mark

Water from aqueous magnesium sulfate.

How did you do?

4d1 mark

Potassium chloride from aqueous potassium chloride.

How did you do?

4e1 mark

Silver chloride from a mixture of silver chloride and water.

How did you do?

Did this page help you?

5a1 mark

The following techniques are used to separate mixtures.

A   simple distillation B   fractional distillation C   evaporation
D   chromatography E   filtration F   diffusion

From this list, choose the most suitable technique to separate the following.

methane from a mixture of the gases, methane and ethane.

How did you do?

5b1 mark

Water from aqueous magnesium sulfate.

How did you do?

5c1 mark

Iron filings from a mixture of iron filings and water.

How did you do?

5d1 mark

Zinc sulfate crystals from aqueous zinc sulfate.

How did you do?

5e1 mark

Hexane from a mixture of the liquids, hexane and octane:

How did you do?

Did this page help you?

6a1 mark

Nerol can be extracted from some plants.

Crushed plant leaves containing nerol are mixed with an organic solvent called octane.

Nerol dissolves in octane.

Describe how you would separate the crushed plant leaves from the solution of nerol in octane.

How did you do?

6b2 marks

The boiling point of nerol is 224 °C.

The boiling point of octane is 126 °C.

Explain how distillation separates nerol from the octane.

How did you do?

6c2 marks

The mixture of coloured compounds in plant leaves can be separated by chromatography.

The apparatus is shown.

 
q7d_0620-s20-qp-32_cie-igcse-chemistry
 

On the diagram:

●   draw an ‘X’ to show where the mixture of coloured compounds is placed at the start of the experiment
●   draw a line to show the level of the solvent at the start of the experiment.

How did you do?

Did this page help you?