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Oxidising Power and Displacement
Oxidising power of the halogens falls down Group 17: F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen displaces a less reactive halide from aqueous solution. Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
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Oxidising Power and Displacement
What is it?
Oxidising power of the halogens falls down Group 17: F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen displaces a less reactive halide from aqueous solution. Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
In simple words
- Oxidising power: F₂ > Cl₂ > Br₂ > I₂.
- Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
- Write ionic equations; use colour as evidence.
What you should learn
- Explain Oxidising Power and Displacement using Group 17 language.
- Link trends to size, shielding, forces and bond strength.
- Apply equations and observations in FBISE-style answers.
Recommended for Class 11
Full school-level explanation
Oxidising power of the halogens falls down Group 17: F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen displaces a less reactive halide from aqueous solution. Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
Beginner
Stronger halogen pushes out weaker halide from solution. Order of strength: F₂ > Cl₂ > Br₂ > I₂. Cl₂ can free Br₂ or I₂; Br₂ can free I₂; I₂ cannot free Cl₂ or Br₂.
Intermediate
Write ionic equations and predict colour: Br₂ orange/red-brown; I₂ brown (aq) or violet (organic). Remember I₂ does not displace Cl⁻/Br⁻. Separate oxidising power (X₂) from reducing power of halides (I⁻ strongest reductant of Cl⁻/Br⁻/I⁻).
Advanced
Down the group, larger atoms hold the gained electron less tightly (lower electronegativity / less favourable electron gain in the school story), so oxidising power falls. Conversely, I⁻ is the strongest reductant of the common triad. Fluorine’s extreme oxidising power is a named trend extreme, not a student bench reagent.
Remember
F₂>Cl₂>Br₂>I₂ oxidising · Cl₂ displaces Br⁻/I⁻ · Br₂ displaces I⁻ · I₂ does NOT displace Cl⁻/Br⁻ · X₂ ≠ X⁻.
Deeper understanding
Go deeper on Oxidising Power and Displacement: connect the definition to reasons, relationships, exceptions, and exam wording.
Common mistakes
Exam focus
Oxidising order
Displacement rules
Key equations
Observation
Exam focus
Quick revision
- Beginner: Stronger halogen pushes out weaker halide from solution. Order of strength: F₂ > Cl₂ > Br₂ > I₂. C
- Intermediate: Write ionic equations and predict colour: Br₂ orange/red-brown; I₂ brown (aq) or violet (organic). R
- Oxidising power: F₂ > Cl₂ > Br₂ > I₂.
- Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
- Write ionic equations; use colour as evidence.
For long answers on Oxidising Power and Displacement: define clearly → explain the main parts → give one example → state one exam caution.
Exam Focus
Exam Focus
Important points
- Beginner: Stronger halogen pushes out weaker halide from solution. Order of strength: F₂ > Cl₂ > Br₂ > I₂. C
- Intermediate: Write ionic equations and predict colour: Br₂ orange/red-brown; I₂ brown (aq) or violet (organic). R
- Oxidising power: F₂ > Cl₂ > Br₂ > I₂.
- Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
Common exam traps
- Saying I₂ displaces chlorine or bromine from solution.
- Confusing halogen X₂ with halide X⁻ in equations.
Long question structure
Definition → key parts → example → exam caution
Common Mistakes
Common Mistakes
- Mistake
Saying I₂ displaces chlorine or bromine from solution.
- Mistake
Confusing halogen X₂ with halide X⁻ in equations.
- Mistake
Reversing the oxidising order (putting I₂ strongest).
- Mistake
Forgetting the colour observation that proves displacement.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Beginner: Stronger halogen pushes out weaker halide from solution. Order of strength: F₂ > Cl₂ > Br₂ > I₂. C
Intermediate: Write ionic equations and predict colour: Br₂ orange/red-brown; I₂ brown (aq) or violet (organic). R
Oxidising power: F₂ > Cl₂ > Br₂ > I₂.
Cl₂ displaces Br⁻ and I⁻; Br₂ displaces I⁻; I₂ does not displace Cl⁻ or Br⁻.
Oxidising power of the halogens falls down Group 17: F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen displaces a less reactive halide from aqueous solution. Cl₂ di
- Definition
- Oxidising power of the halogens falls down Group 17: F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen displaces a less reactive halide from aqueous solution. Cl₂ di
- Critical warning
- Saying I₂ displaces chlorine or bromine from solution.
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Exam Practice
Define
Q1. Define Oxidising Power and Displacement.
Explain
Q2. Explain: Beginner.
Example
Q3. Give one clear example of Oxidising Power and Displacement and say why it fits.
Mistake
Q4. State one common mistake students make about Oxidising Power and Displacement.
Exam note
Q5. Write a short exam note on Oxidising Power and Displacement: definition, two points, one example.
Sources & References
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.