CBSE Class 11-science Answered
In most situations of balancing an equation, you are not told whether the reaction is redox or not.
In these circumstances, you can use a procedure called the oxidation number method.
The skeleton equation is:
I2 + HNO3 → HIO3 + NO2 + H2O
Step 2
The oxidation number of various atoms involved in the reaction.
0 +1 +5 -2 +1 +5 -2 +4 -2 +1 -2
I2 + HNO3 → HIO3 + NO2 + H2O
Step 3
For N oxidation number changes from +5 to +4 so it is reduced. For I oxidation number changes from 0 to +5 so it is oxidized. No change in oxidation number of O.
Step 4
Determine the net increase in oxidation number for the element that is oxidized and the net decrease in oxidation number for the element that is reduced.
For I 0 to +5 Net change = +5 ......... Oxidation
For N +5 to +4 Net change = -1 ..........Reduction
Step 5
Determine a ratio of oxidized to reduced atoms that would yield a net increase in oxidation number equal to the net decrease in oxidation number.
I atoms would yield a net increase in oxidation number of +5. (five electrons would be lost by five I atoms.). 1 N atom would yield a net decrease of -1. (One N atom would gain three electrons.)
Thus the ratio of I atoms to N atoms is 5:1.But we have I2 as a reactant then the ratio becomes 10:1
Step 6
To get the ratio identified in Step 5, add coefficients to the formulas which contain the elements whose oxidation number is changing.
and we will get the balanced equation,
I2 + 10 HNO3 → 2HIO3 + 10NO2 + 4H2O