Applications of Chlorine

Anexos:

• Group 7 - Halogens

1. Bleach (NaClO)
   1. 2NaOH + Cl2 --> NaClO + NaCl + H2O
      1. DISPROPORTIONATION REACTION - chlorine is oxidised and reduced
2. Water Treatment
   1. Cl2 + H20 --> 2H+ + Cl- + ClO-
      1. chlorate(I) ions kill bacteria
      2. Cl2 + H2O --> HOCl + HCl
         1. H0Cl -sunlight-> O2 + 2HCl
   2. Cl2 + H2O --> 4H+ + Cl- + O2
   3. POSITIVES
      1. kills pathogens
      2. some chlorine doesn't react until later, preventing reinfection further on
      3. prevents growth of algae and discolouration caused by organic compounds
      4. removes bad tastes and smells
   4. NEGATIVES
      1. chlorine gas is very harmful if inhaled
      2. liquid chlorine can cause severe chemical burns
      3. can react with organic compounds in water to form chlorinated hydrocarbons which are carcinogenic
         1. e.g. CH3Cl
         2. however, increased cancer risk is small compared to risks from untreated water