Characteristic Reactions of Halogens
1. Reactions with Hydrogen
Halogens react directly with hydrogen to form hydrogen halides. The reactivity varies among halogens:
- Fluorine (F₂): Vigorous reaction
- Chlorine (Cl₂): Reacts in presence of light
- Bromine (Br₂): Reacts readily
- Iodine (I₂): Reversible reaction
H₂ + X₂ → 2HX
H₂ + I₂ → 2HI2. Reactions with Other Elements
- F₂ ignites elements like K, B, Si, P, S, I spontaneously.
- Cl₂ reacts with most metals and non-metals (except C, N₂, and O₂).
- Br₂ reacts with alkali metals and elements like P, As, Sb.
- I₂ is less reactive but forms iodides with Ag, Au, Al.
2Fe + 3F₂ → 2FeF₃
2Fe + 3Cl₂ → 2FeCl₃
Fe + Cl₂ → FeCl₂3. Reaction with Water
Fluorine reacts vigorously with water:
F₂ + 2H₂O → 4HF + O₂
3F₂ + 3H₂O → 6HF + O₃Chlorine and bromine react to form a mixture of acids:
Cl₂ + H₂O → HCl + HClO
2Br₂ + H₂O → 4HBr + O₂Iodine does not react due to high lattice energy.
4. Disproportionation Reactions
Halogens undergo disproportionation where the same element is both oxidized and reduced:
X₂ + H₂O → HX⁻¹ + HOX⁺¹
Cl₂ + H₂O → HCl + HOCl
Cl₂ + 2OH⁻ → Cl⁻ + ClO⁻ + H₂O5. Reactions with Alkali
In cold and hot states, halogens react differently with alkali:
Cold:
X₂ + 2NaOH → NaX + NaXO + H₂O
Hot:
X₂ + 6NaOH → 5NaX + NaXO₃ + 3H₂OFluorine reaction:
2F₂ + 4NaOH → 2NaF + OF₂ + H₂O
(Concentrated) → 4NaF + 2H₂O + O₂6. Reactions with Hydrogen Sulphide (H₂S)
All halogens react with hydrogen sulfide to form hydrogen halides and sulfur:
X₂ + H₂S → 2HX + S
Example: Cl₂ + H₂S → 2HCl + S
Tags
Characteristic Reactions of Halogens
Disproportionation Reactions
Halogen and Metal Reactions
Halogen Reactions with Water
Halogens with Alkali
Halogens with H2S
Halogens with Hydrogen