16.0 CHLORINE AND ITS COMPOUNDS

Chlorine is a member of the halogen family (Group VII). It is a highly reactive, greenish-yellow gas with a pungent odor. Chlorine and its compounds have numerous applications, from water purification and bleaching to the production of hydrochloric acid and PVC. This chapter explores the laboratory preparation and properties of chlorine, the chemistry of hydrogen chloride and hydrochloric acid, and the industrial manufacture of sodium hypochlorite (bleach).

16.1 CHLORINE (Cl₂)

16.1.1 Laboratory Preparation of Chlorine

Chlorine is typically prepared in the laboratory by oxidizing concentrated hydrochloric acid using a strong oxidizing agent like manganese(IV) oxide (MnO₂) or potassium permanganate (KMnO₄).

Method A: Using Manganese(IV) Oxide (MnO₂)

• Reactants: Manganese(IV) oxide (black powder) and concentrated hydrochloric acid.
• Equation: MnO₂(s) + 4HCl(aq) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)
• Procedure:
  1. MnO₂ is placed in a round-bottom flask.
  2. Concentrated HCl is added through a thistle funnel.
  3. The mixture is warmed gently. Chlorine gas is evolved.
  4. Chlorine is denser than air and moderately soluble in water, so it is collected by upward displacement of air (downward delivery) or by downward delivery into a gas jar. It can also be collected over saturated brine (concentrated salt solution) because it is less soluble in brine than in water.
• Dryi