Identifying Transition Metal Ions (Oxford AQA International A Level Chemistry)

Revision Note

Richard Boole

Written by: Richard Boole

Reviewed by: Stewart Hird

Required Practical 9: Transition Metal Ions in Aqueous Solution

Objective

To carry out simple test–tube reactions to identify transition metal ions in aqueous solution.

Apparatus

  • Solution Q

  • Solution R

  • Solution S

  • 1.0 mol dm-3 sodium hydroxide solution

  • 1.0 mol dm-3 sodium carbonate solution

  • 0.05 mol dm-3 silver nitrate solution

  • 12 test tubes

  • Test-tube rack

  • 7 dropping pipettes

  • 250 cm3 beaker

  • Hot water

  • Distilled / deionised water

Method

Test 1 - part a

  • Note the initial colour of solution Q

  • Place 10 drops of solution Q in a test tube

  • Add sodium hydroxide solution, dropwise with gentle shaking, until in excess

  • Keep the test tube for part b

  • Record any observations in an appropriate table

  • Repeat this test with solutions R and S

Test 1 - part b

  • Half fill a 250 cm3 beaker with freshly boiled water

  • Stand the three test tubes from part a in the beaker of hot water for about 10 minutes

  • Record any observations in an appropriate table

Test 2

  • Place 10 drops of sodium carbonate solution in a test tube

  • Add 10 drops of solution Q

  • Shake the mixture gently

  • Record any observations in an appropriate table

  • Repeat this procedure with solutions R and S

Test 3

  • Place about 10 drops of solution Q in a test tube

  • Add about 10 drops of silver nitrate solution and shake the mixture gently

  • Repeat this procedure with solutions R and S

  • Allow the three test tubes to stand for about 10 minutes

  • Record any observations in an appropriate table

Practical Tip

  • Always use clean test tubes and pipettes as the tests are very sensitive and you don't want to cross-contaminate the solutions

  • It's a good idea to label your test tubes to avoid confusing ones that have the same appearance, especially when they are in a water bath and not arranged in a test tube rack

  • To observe colour changes more clearly, using a white background such as a piece of paper can help

Results

  • The results for this required practical are the observations of solutions Q, R and S in tests 1, 2 and 3

  • A suitable results table could be:

Test

Q

R

S

1a - Initial colour

1a - Add NaOH (aq)

1a - Stand in water bath

2 - Add Na2CO3 (aq)

3 - Add AgNO3 (aq)

Evaluation

  • The results from all three tests are used to identify the ions present in solutions Q, R and S

Worked Example

The following tests were completed on solutions Q, R and S. The results are shown in the table.

Test

Q

R

S

Initial colour

yellow solution

light blue solution

pale green solution

Add NaOH (aq)

orange/brown precipitate

blue precipitate

grey/green precipitate

Add excess NaOH (aq)

no visible change

no visible change

no visible change

Add Na2CO3 (aq)

orange/brown precipitate and effervescence

blue green precipitate

grey/green precipitate

Add AgNO3 (aq)

no visible change

white precipitate

no visible change

Identify the anions and cations present, where possible, in solutions Q, R and S.

Answers: 

  • Solution Q - 0.2 mol dm-3 iron(III) nitrate solution

  • Solution R - 0.2 mol dm-3 copper(II) chloride solution

  • Solution S - 0.5 mol dm-3 ammonium iron(II) sulfate solution

Solution Q

  • Test 1 results

    • Yellow solution suggests a Fe3+ cation

    • Orange brown precipitate with NaOH (aq) suggests a Fe3+ cation

    • No further change with excess NaOH (aq) suggests a Fe3+ cation

  • Test 2 results

    • Orange/brown precipitate and effervescence suggests a Fe3+ cation

  • Test 3 results

    • No visible change suggests the anion is not a halide ion

  • Anion = cannot be determined

  • Cation = iron(III) / Fe3+

Solution R

  • Test 1 results

    • Light blue solution suggests a Cu2+ cation

    • Blue precipitate with NaOH (aq) = suggests a Cu2+ cation

    • No further change with excess NaOH (aq) suggests a Cu2+ cation

  • Test 2 results

    • Blue/green precipitate and effervescence suggests a Cu2+ cation

  • Test 3 results

    • White precipitate suggests a Cl- anion

  • Anion = chloride / Cl-

  • Cation = copper(II) / Cu2+

Solution S

  • Test 1 results

    • Pale green solution suggests a Fe2+ cation

    • Grey / green precipitate with NaOH (aq) suggests a Fe2+ cation

    • No further change with excess NaOH (aq) suggests a Fe2+ cation

  • Test 2 results

    • Grey/green precipitate suggests a Fe2+ cation

  • Test 3 results

    • No visible change suggests the anion is not a halide ion

  • Anion = cannot be determined

  • Cation = iron(II) / Fe2+

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Richard Boole

Author: Richard Boole

Expertise: Chemistry

Richard has taught Chemistry for over 15 years as well as working as a science tutor, examiner, content creator and author. He wasn’t the greatest at exams and only discovered how to revise in his final year at university. That knowledge made him want to help students learn how to revise, challenge them to think about what they actually know and hopefully succeed; so here he is, happily, at SME.

Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.