  Question

Balance the following redox reactions in basc medium :    $$Mn{ O }_{ 4 }^{ - }+{ I }^{ - }\longrightarrow Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - }$$

A
2MnO4+I+H2O2MnO2+IO3+2OH  B
3MnO4+I+H2O4MnO2+IO3+2OH  C
3MnO4+I+H2O5MnO2+IO3+2OH  D
None of these  Solution

The correct option is A $$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }+{ H }_{ 2 }O\longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - }+2{ OH }^{ - }$$The unbalanced redox equation is as follows:$$Mn{ O }_{ 4 }^{ - }+{ I }^{ - }\longrightarrow Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - }\quad (basic)$$All atoms other than H and O are balanced.The oxidation number of Mn changes from 7 to 4. The change in the oxidation number is 3. The oxidation number of I changes from -1 to 5. The change in the oxidation number  is 6.To balance the increase in the oxidation number with decrease in the oxidation number multiply $$Mn{ O }_{ 4 }^{ - }+{ I }^{ - }$$ and $$Mn{ O }_{ 2 }$$ with 2. $$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }\longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - }\quad (basic)$$To balance O atoms, add one water molecule on RHS. $$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }\longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - } + H_2O\quad (basic)$$To balance H atoms, add 2$$H^+$$ on LHS.$$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }+2H^+ \longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - } + H_2O\quad (basic)$$Since the reaction occurs in basic medium, add 2 $$OH^-$$ ions on either side.$$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }+2H^++2OH^- \longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - } +2OH^-+ H_2O\quad (basic)$$On LHS, 2 $$H^+$$ ions combine with 2 $$OH^-$$ ions to form 2 water molecules out of which one water molecule cancels with one water molecule on RHS.$$2Mn{ O }_{ 4 }^{ - }+{ I }^{ - }+{ H }_{ 2 }O\longrightarrow 2Mn{ O }_{ 2 }+I{ O }_{ 3 }^{ - }+2{ OH }^{ - }$$This is the balanced chemical equation.Chemistry

Suggest Corrections  0  Similar questions
View More  People also searched for
View More 