The chemistry of silver

In this experiment, students can explore the properties of silver compounds, and discover how they interact in redox reactions, complex formation, and colour/state changes.

This practical should take 20 minutes.

Equipment

Apparatus

• Student worksheet

• Clear plastic sheet (eg OHP sheet)

• Piece of black or dark card

• Scissors

• Magnifying glass

Chemicals

• Ammonia solution 3 mol dm^–3

• Iron(II) sulfate 0.2 mol dm^–3

• Potassium bromide 0.2 mol dm^–3

• Potassium iodide 0.2 mol dm^–3

• Silver nitrate 0.1 mol dm^–3

• Sodium chloride 0.2 mol dm^–3

Health, safety and technical notes

• Read our standard health and safety guidance.

• Students must wear suitable eye protection (Splash resistant goggles to BS EN166 3).

• Ammonia solution, 3 mol dm^–3 NH₃(aq) is CORROSIVE and a respiratory irritant (see CLEAPSS HazCard HC006).

• Iron(II) sulfate, 0.2 mol dm^–3, FeSO₄.7H²O(aq), Potassium bromide, 0.2 mol dm^–3, KBr(aq) and Potassium iodide, 0.2 mol dm^–3, KI(aq) are low hazard (see CLEAPSS HazCard HC055B, HC047b).

• Silver nitrate, 0.1 mol dm^–3, AgNO₃(aq) is an eye irritant. Keep separate from organic waste containers (see CLEAPSS HazCard HC087).

Procedure

1. Cover the worksheets with a clear plastic sheet.

2. Put one drop of silver nitrate solution in each box in the top two silver nitrate rows only. (The third row is left empty for now.)

3. Add one drop of each of the chloride, bromide and iodide solutions to the drop of silver nitrate solution in the appropriate box.

4. Make a cover from your piece of card and place it over all the drops in the first row only.

5. Record your observations of the uncovered row.

6. After 15 minutes, remove the cover and compare the covered and uncovered rows.

7. Put one drop of silver nitrate solution in each box in the third silver nitrate row.

8. Add one drop of each of the chloride, bromide and iodide solutions to the drops of silver nitrate solution in the appropriate box on the worksheet.

9. Add five drops of ammonia solution to each of the drops.

10. Stir gently with the tip of a pipette.

11. Record your observations. 

12. Put one drop of silver nitrate solution in the box provided on the worksheet.

13. Add one drop of iron(II) solution.

14. Observe closely using a magnifying glass.

Observations

The addition of chloride, bromide and iodide solutions to silver nitrate solution produces immediate precipitates – white, pale yellow and yellow respectively.

The appearance of the silver halide precipitates is retained if they are covered from the light.

The colours of the silver chloride and bromide gradually darken due to the formation of grey metallic silver, while the iodide appears to be more stable when left exposed to light (artificial or sunlight).

Silver chloride dissolves readily in ammonia solution, while the bromide partially dissolves and the iodide does not.

Adding iron(II) solution to the silver nitrate solution produces a glittering of metallic silver, which can be seen using a magnifying glass. The reaction is: Ag⁺(aq) + Fe²⁺(aq) → Ag(s) + Fe³⁺(aq).

Discussion of this reaction could centre around the respective redox potentials.