IGCSEScienceEdexcelScience (Double Award) (Modular)Chemistry Unit 2Exam Questions6. Inorganic Chemistry: Part 2Chemical tests

Chemical tests (Edexcel IGCSE Science (Double Award) (Modular): Chemistry Unit 2): Exam Questions

Exam code: 4XSD1

1 hour14 questions
Easy
Medium
Hard
1a
1 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.

How did you do?

1b
1 mark

Name the cream precipitate.

How did you do?

1c
1 mark

Identify the white solid.

How did you do?

1d
3 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

How did you do?

2
1 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?

  • Fe3+ and Cl-

  • Fe3+ and SO42-

  • Fe2+ and Cl-

  • Fe2+ and SO42-

Choose your answer

3
1 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?

  • Ammonium ions

  • Chloride ions

  • Sulfate ions

  • Magnesium ions

Choose your answer

4
1 mark

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

  • Anhydrous copper(II) sulfate would turn blue when the solution was added

  • The resulting hydrated copper(II) sulfate would have the chemical formula CuSO4.H2O

  • The boiling point should be 100 °C

  • The boiling point should be sharp, not gradual

Choose your answer

5
1 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 gas is produced which causes cloudiness in limewater

  • A gas is produced which makes a squeaky pop sound when a lit splint is introduced

  • A gas is produced which bleaches damp litmus paper

  • A gas is produced which re-ignites a glowing splint

Choose your answer

1a
3 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

How did you do?

1b
6 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.

How did you do?

2
1 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?

    • Test: flame test

    • Result: blue-green flame

    • Test: add sodium hydroxide solution

    • Result: blue precipitate forms

    • Test: add acidified silver nitrate solution

    • Result: cream precipitate forms

    • Test: add sodium hydroxide solution

    • Result: green precipitate forms

Choose your answer

3a
4 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]

How did you do?

3b
3 marks

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

Test 

Result

How did you do?

3c
6 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.

How did you do?

4
1 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+?

  • Add sodium hydroxide solution

  • A positive test produces a pungent-smelling gas

  • Use dry red litmus paper to test the gas produced

  • The litmus paper should turn blue if NH4+ ions were present 

Choose your answer

1a
3 marks

Hydrated ammonium iron(III) 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.

How did you do?

1b
6 marks

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

Apparatus for heating hydrated ammonium iron(III) sulfate to find x: a horizontal test tube containing the solid is heated over a Bunsen burner, with a delivery tube leading to a second test tube standing in a beaker of ice and water, where the water given off condenses and collects

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 = .....................................

How did you do?

2a
6 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?

2b
4 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]

How did you do?

3a
2 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.

How did you do?

3b
6 marks

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

How did you do?

4
6 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.

How did you do?

5a
3 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]

How did you do?

5b
3 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.

How did you do?

5c
4 marks

The diagram shows the apparatus used to heat ammonium chloride.

Diagram of the apparatus used to heat ammonium chloride: a 100 cm3 conical flask containing ammonium chloride solid is heated on a tripod and gauze over a Bunsen burner, with two pieces of damp litmus paper held by clamps just inside the neck of the flask.

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]

How did you do?

5d
1 mark

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

How did you do?