AQA GCSE Chemistry

Topic Questions

GCSEChemistryAQATopic Questions8. Chemical Analysis8.3 Methods of Identifying Ions

8.3 Methods of Identifying Ions

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11 mark

Scientists test a solution of compound X.

Table 1 shows their results.

Table 1

Test Result
Add dilute nitric acid followed by 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-

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21 mark

Scientists test a solution from a bottle that is known to contain a copper (II) compound.

Table 1 shows their results.

Table 1

Test Result
Flame test Yellow flame
Add sodium hydroxide solution Blue precipitate formed
Add dilute nitric acid followed by silver nitrate solution Yellow precipitate formed

Which statement below is true?

  • The flame test was performed incorrectly

  • Bromide ions are present, so the compound is CuBr2

  • The test tube was contaminated for the sodium hydroxide test

  • The copper compound in the bottle was contaminated with another metal compound

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31 mark

A compound is suspected of containing calcium ions, Ca2+.

Which test would not help to positively identify calcium?

  Test Result
A Flame test Orange-red flame
B Add sodium hydroxide solution White precipitate forms
C Add nitric acid and silver nitrate White precipitate forms
D Flame emission spectroscopy Characteristic lines match the reference spectrum

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41 mark

Which is not an advantage of using instrumental methods rather than small-scale lab methods for identifying ions?

  • Instrumental methods are more accurate

  • Instrumental methods are faster

  • Instrumental methods are cheaper

  • Instrumental methods are more sensitive

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51 mark

Calcium carbonate can react with hydrochloric acid by the following equation:

CaCO3 (s) + 2HCl (aq) rightwards arrowCaCl2 (aq) + H2O (l) + CO2 (g)

Which observation does not tell you that this reaction has occurred?

  Test Result
A Add dilute nitric acid then by silver nitrate solution White precipitate forms
B Bubble any gases present through limewater Limewater turns cloudy
C Observe the solutions when they are mixed Solutions bubble and fizz upon mixing
D Test pH of the solution at the start and after 30 s pH increases

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