Edexcel IGCSE Chemistry

Topic Questions

IGCSEChemistryEdexcelTopic Questions2. Inorganic Chemistry2.8 Chemical Tests

2.8 Chemical Tests

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1a1 mark

A student does these two tests on a solution made from a white solid.

  • flame test
  • add acidified silver nitrate solution

The table shows his results.

Test Result
flame test red flame
add acidified silver nitrate solution cream precipitate

 

Give the formula of the ion that produces the red flame.

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1b1 mark

Name the cream precipitate.

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1c1 mark

Identify the white solid.

 

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1d3 marks

The student uses a clean metal wire in the flame test.

 
i)
State why the wire should be clean when used in the flame test.
 
(1)
 
ii)
The table lists properties of some metals.
 
Add ticks (✔) to the table to show the two properties needed in a metal wire used in a flame test.
 
(2)
 
Property  
good conductor of electricity  
high density  
high melting point  
unreactive  

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21 mark

Scientists test a solution of compound X. The table shows their results.

Test Result
Acidified silver nitrate solution White precipitate
Add sodium hydroxide solution Green precipitate

Which two ions are present in compound X?

  ☐ A Fe3+ and Cl-
  ☐ B Fe3+ and SO42-
  ☐ C Fe2+ and Cl-
  ☐ D Fe2+ and SO42-

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31 mark

A student adds a few drops of dilute nitric acid followed by a few drops of silver nitrate solution to a test tube containing an unknown colourless solution. A white precipitate is seen.

What ions could be present in the solution?

  ☐ A Ammonium ions
  ☐ B Chloride ions
  ☐ C Sulfate ions
  ☐ D Magnesium ions

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41 mark

Which statement is incorrect about testing a sample of suspected pure water?

  ☐ A Anhydrous copper(II) sulfate would turn blue when the solution was added
  ☐ B The resulting hydrated copper(II) sulfate would have the chemical formula CuSO4.H2O
  ☐ C The boiling point should be 100 oC
  ☐ D The boiling point should be sharp, not gradual

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51 mark

A solution containing carbonate ions, CO32-, can be reacted with hydrochloric acid, HCl, and a gaseous product collected and tested.

Which is a correct positive test result for a product of this reaction?

  ☐ A A gas is produced which causes cloudiness in limewater
  ☐ B A gas is produced which makes a squeaky pop sound when a lit splint is introduced
  ☐ C A gas is produced which bleaches damp litmus paper
  ☐ D A gas is produced which re-ignites a glowing splint

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1a3 marks

Hydrated ammonium iron(Ill) sulfate is a violet solid that has the formula (NH4)2SO4.Fe2(SO4)3.xH2O

The table shows some tests done on three separate samples of the solid.

Test Observation
Dissolve the solid in water and add acidified barium chloride solution.  
Dissolve the solid in water and add sodium hydroxide solution.  
Add sodium hydroxide solution to the solid and warm the mixture.
Test the gas given off with moist universal indicator paper.		  

Complete the table to show the observation made in each test.

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1b
Sme Calculator6 marks

A student needs to find the value of x in the formula (NH4)2SO4.Fe2(SO4)3.xH2O
He uses this apparatus.

q15b-1-june-2019-1c-qp-edexcel-igcse-chemistry

The hydrated solid decomposes when heated gently.
The equation for the reaction is 

(NH4)2SO4.Fe2(SO4)3.xH2O —> (NH4)2SO4.Fe2(SO4)3 + xH2O

The table shows the student's results. 

mass of empty test tube in g  22.04 
mass of test tube and (NH4)2SO4.Fe2(SO4)3.xH2O in g  34.09 
mass of test tube and (NH4)2SO4.Fe2(SO4)3 in g  28.69 

(i)
Calculate the mass of (NH4)2SO4.Fe2(SO4)3 produced by heating.

(1)

mass of (NH4)2SO4.Fe2(SO4)3 = .............................. g 

(ii)
Calculate the mass of water produced.

(1)

mass of water = ..................................... g

(iii)
Calculate the value of x.
[Mr of (NH4)2SO4.Fe2(SO4)3 = 532 and Mr of H2O = 18]
Give your answer to the nearest whole number.

(4)

Value of x = .....................................

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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.

 

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2b4 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)
 
iii)
Draw a dot‐and‐cross diagram to show the bonding in a molecule of ammonia.
 
Show outer electrons only.
 
(2)

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3a2 marks

A student is given a mixture of two white solid compounds, and a colourless solution containing the same two compounds.

The student is told that one of the compounds is a halide and that the other compound is a carbonate.

Give two reasons why the student should know, without doing any tests, that one of the compounds cannot be copper(II) carbonate.

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3b6 marks

Describe tests the student could do to show that the mixture contains potassium carbonate and potassium iodide.

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46 marks

A technician finds a white solid in an unlabelled beaker.

She knows that the solid is one of the following substances:

  • potassium chloride
  • potassium sulfate
  • sodium chloride
  • sodium sulfate.

Describe how the technician can use chemical tests to identify the solid in the beaker.

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5a3 marks

This question is about ammonium compounds.

The table shows the names and formulae of some ammonium compounds.

 
Name Ammonium nitrate Ammonium carbonate  
Formula NH4NO3   NH4Cl
 
i)
Complete the table by giving the missing information.
 
(2)
 
ii)
When ammonia reacts with nitric acid, ammonium nitrate is formed.
 
Write a chemical equation for this reaction.
 
(1)

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5b3 marks

When ammonium chloride is heated, it undergoes thermal decomposition to form two gaseous products. 

Describe the result of testing each product with damp universal indicator paper.

 

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5c4 marks

The diagram shows the apparatus used to heat ammonium chloride.

 
nh4cl-thermal-decomposition-testing
 
i)
Suggest why the damp litmus paper is two different colours.
 
(1)
 
ii)
Explain what happens to the damp litmus paper as the ammonium chloride is heated. 
 
(3)

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5d1 mark

Explain why a fine white powder formed on the inside of the neck of the conical flask in part (c).

 

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1a
Sme Calculator2 marks

The gas burned in a Bunsen burner is methane.

The equation for the complete combustion of methane is

CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)

Calculate the mass of oxygen required to react with 32 g of methane.

 
[Mr of methane = 16]
 
 
mass of oxygen = .............................. g

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1b7 marks

The diagram shows methane burning in air. It also shows how the two gases formed are collected and tested.

 
products-of-combustion-edexcel-2019ju1c
 
i)
Explain why water collects in the U-tube.
 
(2)
 
ii)
Describe how anhydrous copper(II) sulfate is used to test for water.
 
(2)
 
iii)
Explain the change in the appearance of the limewater.
 
(3)

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2a3 marks

This question is about salts.

When solutions of salts are mixed together, precipitates sometimes form.

The insoluble salt barium carbonate forms as a precipitate when solutions of the soluble salts ammonium carbonate and barium chloride react together.

When solutions of the soluble salts potassium chloride and magnesium sulfate are mixed, no precipitate forms.

Complete the table to show the results of mixing solutions of some soluble salts.

  ammonium carbonate solution magnesium sulfate solution
barium chloride solution precipitate of barium carbonate  
potassium chloride solution   no precipitate
calcium chloride solution   precipitate of calcium sulfate

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2b6 marks

A student has four unlabelled beakers, each containing a colourless solution of a different salt.

The four solutions are

  • potassium carbonate
  • potassium chloride
  • potassium iodide
  • sodium chloride

Describe a method to identify each solution.

Do not refer to safety in your answer.

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31 mark

A compound is suspected of containing copper ions, Cu2+ and bromide ions, Br-.

Which test would not help to positively identify copper ions or bromide ions?

  ☐ A Test: flame test  Result: blue-green flame
  ☐ B Test: add sodium hydroxide solution Result: blue precipitate forms
  ☐ C Test: add acidified silver nitrate solution Result: cream precipitate forms
  ☐ D Test: add sodium hydroxide solution Result: green precipitate forms

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4a4 marks

This question is about elements in Group 7 of the Periodic Table and their compounds.

i)
Give the name of this group of elements.
(1)

ii)
State the colour of chlorine gas.
(1)

iii)
Give a test for chlorine gas.
(2)

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4b3 marks

Give a test to show that a solution contains iodide ions.

Test 

Result

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4c6 marks

A student compares the reactivity of the elements bromine, chlorine and iodine. He mixes these pairs of solutions and observes the reactions that occur.

  • chlorine solution and potassium bromide solution
  • bromine solution and potassium iodide solution

Explain how the reactions can be used to show the order of reactivity of the three elements. Include the colour change that the student would observe in each reaction.

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51 mark

Ammonium ions, NH4+, in a solution can be identified by a chemical test.

Which statement is incorrect about the test for the ammonium ion, NH4+?

  ☐ A Add sodium hydroxide solution
  ☐ B A positive test produces a pungent-smelling gas
  ☐ C Use dry red litmus paper to test the gas produced
  ☐ D The litmus paper should turn blue if NH4+ ions were present 

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