Uses of chlorine and chlorate(I)

• Reaction of chlorine with water to form chloride ions:

  Chlorine is slightly soluble in water, resulting in a pale green solution. Some chlorine reacts with the water to form a mixture of hydrochloric acid and chloric(I) acid. 

  $Cl_2(g)+$$H_2O(l)\ \leftrightarrow\ HCl(aq)+$$HClO(aq)$
• What is $HClO$ used for?


  $HClO$ kills microorganisms and it is used to sterilise drinking water and water in swimming pools.
• What is the advantage of using chlorine in water supplies?

  The benefits of using chlorine in drinking water and in water in swimming pools far outweighs the potential health risks to humans if it were not present. Furthermore, only low concentrations of chlorine are used as a higher concentration would be toxic.
• Chlorine reacts with cold, dilute, aq sodium hydroxide to produce chlorate(I) ions.

  $2NaOH+$$Cl_2\rightarrow\ NaCl+$$NaClO+$$H_2O$

  You would observe a yellow-green gas which forms a colourless solution.

  Ionic equation: $2OH^-+$$Cl_2\rightarrow\ Cl^-+$$ClO^-+$$H_2O$

  This is a redox reaction as chlorine is oxidised from the oxidation state 0 to +1 and chlorine is also reduced from 0 to -1.
• What is the use of a solution containing sodium chlorate(I) ions?

  A solution containing sodium chlorate(I) ions is used as bleach, which kills bacteria and other microorganisms.
• In bright sunlight, chlorine reacts with water to produce a solution containing chloride ions and oxygen.

  Overall equations:

  $2Cl_2(g)+$$2H_2O(l)\ \rightarrow\ 4HCl(aq)+$$O_2(g)$

  OR $2Cl_2(g)+$$2H_2O(l)\ \rightarrow\ 4H^+$$(aq)+$$4Cl^-(aq)+$$O_2(g)$

  Intermediate equation: The UV radiation breaks down the $HClO$ into $HCl$ and $O_2$.

  $2HClO(aq)\ \rightarrow\ 2HCl(aq)+$$O_2(g)$
• Societal advantages and disadvantages of using sodium fluoride and other fluorine containing compounds in drinking water.

  Fluoride ions can help to prevent tooth decay as they strengthen enamel but some people object to this as there may be other health risks associated with fluoride and also because it can be viewed as mass medication.