Question

How would you obtain pure chloroform in the laboratory?

Answer 1

1. Preparation: Chloroform can be prepared in the lab by the reaction of ethanol (or acetone) with bleaching powder (calcium hypochlorite, Ca(OCl)₂).
2. Chemical Reaction: When ethanol reacts with bleaching powder, 
   \[\mathrm{C_2H_5OH} + 3 \mathrm{Ca(OCl)_2} \rightarrow \mathrm{CHCl_3} + \ce{other products}\]
   Alternatively, using acetone:
   \[\mathrm{CH_3COCH_3} + 3 \mathrm{Ca(OCl)_2} \rightarrow \mathrm{CHCl_3} + \ce{other products}\]
3. Separation: The reaction mixture forms layers; separate the chloroform layer by decantation.
4. Purification: Wash the crude chloroform with sodium carbonate (Na₂CO₃) solution to remove acidic impurities. Dry the chloroform using anhydrous calcium chloride (CaCl₂).
5. Distillation: Distill the dried chloroform to remove any remaining impurities and obtain pure chloroform.