Edexcel AS Chemistry

Topic Questions

ASChemistryEdexcelTopic Questions2. Inorganic Chemistry2.2 Groups 1 & 2

2.2 Groups 1 & 2

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1a1 mark

Barium ions can be identified by their flame colour.

Which of the following should be used for a flame test on barium carbonate?

  ☐ A iron wire and water
  ☐ B iron wire and concentrated hydrochloric acid
  ☐ C nichrome wire and water
  ☐ D nichrome wire and concentrated hydrochloric acid

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1b1 mark

What colour do barium ions give in a flame test?

  ☐ A green
  ☐ B lilac
  ☐ C red
  ☐ D yellow

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1c1 mark

A flame test was carried out on a mixture of barium chloride and magnesium chloride.

How does the presence of magnesium ions affect the appearance of the flame colour of barium ions?

  ☐ A the colour is more intense
  ☐ B a bright white colour completely masks the barium colour
  ☐ C there is no change
  ☐ D the barium colour is decreased by the white magnesium flame colour

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2a1 mark

This question is about trends within Group 2 of the Periodic Table.

Which of the following describes the trends in thermal stability of the Group 2 carbonates and nitrates going down the group?

      Thermal stability
      Carbonates Nitrates
  ☐ A increases increases
  ☐ B increases decreases
  ☐ C decreases increases
  ☐ D decreases decreases

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2b4 marks

Describe, with the aid of a labelled diagram, how you would compare the thermal stability of two different Group 2 nitrates using simple laboratory equipment.

Your answer must include one safety precaution (excluding the use of gloves, laboratory coat and eye protection).

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2c1 mark

Which of the following describes the trends in the solubility in water of the Group 2 hydroxides and sulfates going down the group?

      Solubility in water
      Hydroxides Sulfates
  ☐ A increases increases
  ☐ B increases decreases
  ☐ C decreases increases
  ☐ D decreases decreases

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1a2 marks

This question is about flame tests for Group 1 and 2 metal ions.

i)
State the colour of the flame produced by separate samples of potassium and strontium ions.

(1)

Potassium ions ..................................................................................................

Strontium ions....................................................................................................

ii)
Give a reason why carrying out a flame test on a mixture of potassium chloride and strontium chloride does not clearly show that two different metal ions are present.

(1)

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1b5 marks

In the first stage of the flame test, the nichrome wire is dipped into concentrated hydrochloric acid and then heated in a Bunsen flame.

In the second stage, this nichrome wire is dipped into fresh hydrochloric acid and then into the metal salt to be tested before being reheated in the Bunsen flame.

i)
Give two reasons why the wire is made of nichrome and not iron.

(2)

ii)
Give a reason why the wire is dipped into acid and then heated in the first stage.

(1)

iii)
State why fresh concentrated hydrochloric acid is used in the second stage of the flame test.

(1)

iv)
State why hydrochloric acid is used in the second stage of the flame test.

(1)

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1c3 marks

Explain, with reference to electron transitions, the formation of the colour in a flame test.

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2a5 marks

Thermal decomposition is the breaking down of a substance by heat.  

An experiment was carried out to investigate the thermal decomposition of a metal nitrate using the apparatus shown. 

q4a-9cho-al-1-june-2019-qp-edexcel-a-level-chem
i)
The glowing splint is used as a test for one of the gases given off in this experiment.
Identify this gas and the positive result of the test.
(1)

ii)
Give the name and appearance of the other gas given off in this experiment when a Group 2 nitrate is heated.
(1)

iii)
Write the equation for the decomposition if the Group 1 compound, sodium nitrate, was used in this experiment.
State symbols are not required.
(1)

iv)
Describe the apparatus that would be used to compare the decomposition of metal carbonates. Include how the rate of decomposition would be compared.
(2)

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2b3 marks

Explain why magnesium carbonate decomposes much more readily on heating than barium carbonate.

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3a9 marks

A solid, white, water-soluble compound was thought to be magnesium bromide.
A student carried out tests to confirm the identity of both ions present.

A flame test was carried out to test for the cation.

i)
Describe how a flame test is carried out.

(3)

ii)
Explain the origin of flame test colours.

(4)

iii)
Give a reason why the magnesium ion does not produce a flame colour.

(1)

iv)
Give a reason why the lack of a flame colour is not a positive test for the magnesium ion.

(1)

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3b2 marks
i)
Give the formula of a reagent that would produce a cream-coloured precipitate when added to an aqueous solution of magnesium bromide.

(1)

ii)

The identity of the anion may be confirmed by testing the solubility of the cream-coloured precipitate in ammonia solution. Which pair of responses helps to confirm the identity of the anion?

(1)

      Solubility in dilute
ammonia solution		 Solubility in concentrated
ammonia solution
  ☐ A insoluble insoluble
  ☐ B insoluble soluble
  ☐ C soluble insoluble
  ☐ D soluble soluble

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4a2 marks

The nitrates of lithium, rubidium and strontium are all white solids. The compounds are held together by ionic bonds.

State the meaning of the term ‘ionic bond’.

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4b
Sme Calculator1 mark

What is the percentage by mass of strontium in strontium nitrate?

  ☐ A 38.0%
  ☐ B 41.4%
  ☐ C 58.6%
  ☐ D 74.5%

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4c3 marks

These three compounds cannot be identified with certainty from a flame test as the colours seen are similar.
Concentrated hydrochloric acid is used in a flame test procedure.

i)
Which of the following is a reason for dipping the flame test wire in concentrated hydrochloric acid during a flame test procedure?
(1)
  ☐ A it dissolves metal ions from the wire
  ☐ B it neutralises hydroxide ions that might colour the flame
  ☐ C it reduces the metal ions to metal atoms
  ☐ D it reacts with the compounds to form volatile chlorides

ii)
The flame colour given by these three solids in the flame test are shades of
(1)
  ☐ A green
  ☐ B lilac
  ☐ C red
  ☐ D yellow

iii)
What is the best explanation for why metal ions produce different flame colours?
(1)
Different wavelengths of light energy are

  ☐ A required to promote electrons to higher energy levels
  ☐ B released because electrons move from lower to higher energy levels
  ☐ C released due to different gaps between energy levels
  ☐ D required for electron transfer from non-metal ions to metal ions

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4d6 marks

Devise a procedure to identify the nitrates of lithium, rubidium and strontium using the effect of heat on the three solids and any precipitation reactions of the compounds.

Practical details are not required, but you should give the observations expected in each case.

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5a2 marks

This question is about the thermal stability of Group 1 and Group 2 nitrates and carbonates.

Complete the equations for the thermal decomposition of sodium nitrate, NaNO3 , and for the thermal decomposition of calcium nitrate, Ca(NO3)2 .

State symbols are not required.

NaNO3 →

Ca(NO3)2 →

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5b3 marks

The thermal stability of Group 1 nitrates increases down the group.
The decomposition temperatures of some Group 1 nitrates are shown.

Name Formula

Decomposition temperature   / K
sodium nitrate NaNO3 653
potassium nitrate KNO3 673
caesium nitrate CsNO3 687

Explain why the thermal stability of caesium nitrate is greater than that of sodium nitrate.

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5c3 marks

Calcium carbonate is thermally decomposed during the manufacture of cement.

i)
Write an equation, including state symbols, for the thermal decomposition of calcium carbonate.

(1)

ii)
Name all the types of bond present in calcium carbonate.

(1)

iii)
Give a reason, in terms of the bonding, why a high decomposition temperature is required.

(1)

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