CBSE Class 11-science Answered
MO4 minus + I gives MnO2+I2
The skeleton equation is:
MnO4- + I- → MnO2 + I2
The oxidation number of various atoms involved in the reaction.
+7 -2 -1 +4 -2 0
Mn O4- + I- → Mn O2 + I2
For Mn oxidation number changes from +7 to +4 so it is reduced. For I oxidation number changes from -1 to 0 so it is oxidised. No change in oxidation number of O.
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 -1 to 0 Net change = +1
For Mn +7 to +4 Net change = -3
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 +3. (Three electrons would be lost by three I atoms.). 1 Mn atom would yield a net decrease of -3. (One Mn atom would gain three electrons.)
Thus the ratio of I atoms to Mn atoms is 3:1.
To get the ratio identified in Step 5, add coefficients to the formulas which contain the elements whose oxidation number is changing.
MnO4- + 3I- → MnO2 + I2
Still, the equation is not balanced as the charge is different on both sides, so follow step 7.
Balance the rest of the equation by inspection.
If we place a 3 in front of the I- and balance the iodine atoms with a 3/2 in front of the I2, both the atoms and the charge will be balanced.
MnO4- + 3I- → MnO2 + 3/2I2
Multiply by 2 to whole equation and we will get the balanced equation,
2MnO4- + 6I- → 2MnO2 + 3I2
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