1.2 - Redox Reactions of Group VII Elements and Displacement Reactions of Metals

Experiment Summary

This experiment investigates two main chemical processes:

(a) Redox reactions of Group VII elements (halogens) – reactions between chlorine, bromine, and iodine with their halide salts.

(b) Displacement reactions of metals – how magnesium and zinc displace copper from copper(II) sulfate, demonstrating the reactivity of metals based on the electrochemical series.

Materials and Apparatus Required

Chemicals

For Redox Reactions of Halogens:
- Chlorine solution
- Bromine solution
- Iodine solution
- Sodium chloride solution
- Sodium bromide solution
- Potassium iodide solution
- Iron(II) sulfate solution
- Sodium sulfite solution
For Displacement Reactions:
- Acidified copper(II) sulfate solution
- Zinc powder
- Magnesium ribbon

Apparatus

Safety glasses
PVC gloves
Pasteur pipettes
Test tubes and rack
Boiling tubes
Sandpaper (to clean magnesium ribbon)
Fume cupboard (for handling chlorine and bromine)
Bunsen burner

Safety Precautions

Wear safety glasses at all times.
Chlorine and bromine are poisonous. Work in a fume cupboard to avoid inhalation.
Iodine can irritate the skin; handle it with care.
Concentrated hydrochloric acid and sulfuric acid are corrosive to the skin and eyes.
Sodium hydroxide is caustic and harmful to the skin and eyes.
Silver nitrate is hazardous to the eyes and will stain the skin.
Dispose of all chemical waste responsibly by neutralizing it with water and proper dilution.

Method

Redox Reactions of Halogens:

In separate test tubes, mix:

Chlorine with bromide and iodide ions.
Bromine with iodide ions.

Observe and record the colour changes.
Test reactions of halogens with iron(II) sulfate and sodium sulfite.

Chlorine will oxidize $Fe²⁺$ to $Fe³⁺$ , and oxidize $SO₃²⁻$ to $SO₄²⁻$

Displacement Reactions of Metals:

Half-fill two boiling tubes with acidified copper(II) sulfate solution.
Add magnesium ribbon to one tube and zinc powder to the other.
Observe the reactions and note any colour changes and gas evolution.

Results

Redox Reactions of Halogens:

Chlorine oxidizes bromide ions to form $Br₂$ (orange) and iodide ions to form $I₂$ (brown).
Bromine oxidizes iodide ions to $I₂$ .

Displacement Reactions of Metals:

Both magnesium and zinc displace copper, producing a brown precipitate of copper and a colourless solution of magnesium or zinc sulfate.

Example Questions with Answers

infoNote

Q1: Write out the full list of equations for the redox reactions of the halogens.

Chlorine and bromide ions:

Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂

Oxidation state changes: $Cl\ 0 → -1$ (reduced), $Br -1 → 0$ (oxidised)

Chlorine and iodide ions:

Cl₂ + 2I⁻ → 2Cl⁻ + I₂

Oxidation state changes: $Cl\ 0 → -1$ (reduced), $I -1 → 0$ (oxidised)

Bromine and iodide ions:

Br₂ + 2I⁻ → 2Br⁻ + I₂

Oxidation state changes: $Br 0 → -1$ (reduced), $I -1 → 0$ (oxidised)

infoNote

Q2: Explain why magnesium is more reactive than zinc.

Magnesium has a larger atomic radius and less nuclear charge, making it easier for magnesium to lose electrons compared to zinc.

Therefore, magnesium is higher up in the electrochemical series and more reactive.

infoNote

Q3: What happens when copper wire is suspended in a solution of silver nitrate?

Crystals of silver will form on the copper wire, and the solution will turn blue as copper(II) ions ( $Cu²⁺$ ) are released into the solution.

- Redox Reactions of Group VII Elements and Displacement Reactions of Metals Simplified Revision Notes for Leaving Cert Chemistry

1.2 - Redox Reactions of Group VII Elements and Displacement Reactions of Metals

Experiment Summary

Materials and Apparatus Required

Chemicals

Apparatus

Safety Precautions

Method

Redox Reactions of Halogens:

Displacement Reactions of Metals:

Results

Redox Reactions of Halogens:

Displacement Reactions of Metals:

Example Questions with Answers

Q1: Write out the full list of equations for the redox reactions of the halogens.

Q2: Explain why magnesium is more reactive than zinc.

Q3: What happens when copper wire is suspended in a solution of silver nitrate?

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