Comprehensive notes on Halogens (Group 17), including Fluorine, Chlorine, Bromine, Iodine. Covers Bleaching Powder, Disproportionation Reactions, Oxyacids, and Interhalogen Compounds.
Included Elements: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At).
General Trends:
1. State: F2, Cl2 (Gases), Br2 (Liquid), I2 (Solid).
2. Oxidizing Power: Decreases down the group (F2 > Cl2 > Br2 > I2). F2 is the strongest oxidizing agent.
Acidic Strength: Increases down the group (HF < HCl < HBr < HI). HF is a weak acid due to strong H-bonding.
Thermal Stability: Decreases down the group (HF > HCl > HBr > HI).
Properties: HF is liquid (due to H-bonding), others are gases.
Disproportionation: A reaction in which the same element is oxidized and reduced.
1. With Cold Dilute NaOH:
Cl2 + 2NaOH → NaCl + NaClO + H2O (Formation of Sodium Hypochlorite).
2. With Hot Conc. NaOH:
3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O (Formation of Sodium Chlorate).
Preparation: Hasenclever Method or Beckmann's Method. Reaction of Chlorine with dry Slaked Lime.
Ca(OH)2 + Cl2 → CaOCl2 + H2O.
Uses: Sterilization of water, bleaching cotton/paper.
Acidity Order: HClO < HClO2 < HClO3 < HClO4.
Reason: As the number of Oxygen atoms increases, the oxidation state of Cl increases, making the O-H bond more polar and H+ easier to remove.