Long Answer Type
Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.Â
The Mn3+ ions is unstable in solution and undergoes disproportionation to give Mn2+, MnO2 and H+ ion. Write a balanced ionic equation for the reaction.
Short Answer TypeLong Answer Type
The skeleton equation is:
Separation of the equation in two half reactions
(i) Write the O.N. of the atoms involved in the equation
  -7 -2      -1         +4 -2   0
  
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(ii) Identify the atoms which undergo a change in O.N.
  +7     -1           +4     0
(iii) Find out the species involved in the oxidation and reduction half-reactions:
Oxidation half-reaction:
          
Reduction half-reaction:
        
Balancing the oxidation half reaction
           
Balancing the reduction half reaction
 The reduction half-reaction is:
            
(i) As the decrease in O.N. is 3, therefore add 3e- on the reactant side
               
(ii) Balance O atoms by adding two H2O molecules on the product sideÂ
        
(iii) Balance the charges, by adding four OH- on the product side and balance H atoms by adding four H2O molecules on the reactant side. 
   Thus, the reduction half-reaction is balanced. Adding the two half reactions. In order to equate the electrons, multiply equation. (i) by 3 and equation, (ii) by 2 and add the two equations.
Permanganate (VII) ion, 
 in basic solution oxidises iodide ion, I- to produce molecule iodine (I2) and manganese (IV) oxide (MnO2). Write a balanced ionic equation to represent redox reaction.Â
Balance the following equations in basic medium by ion-electron method and oxidation number method:
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