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8.21  The Mn^{3+}  ion is unstable in solution and undergoes disproportionation to give Mn^{2+} , MnO_{2} and H^{+} ion. Write a balanced ionic equation for the reaction

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Answer-

The base equation 

Mn^{3+}\rightarrow Mn^{2+}+MnO_{2}+H^{+}

write oxidation half with their oxidation state

Mn^{3+}(+3)\rightarrow MnO_{2}(+4)

Balance the charge on Mn by adding 1 e^{-} on RHS side. To balance charge add H^{+} ions on RHS side and then for oxygen balance add H_{2}O molecule on LHS side.

Mn^{3+}+2H_{2}O\rightarrow MnO_{2}+1e^{-}+4H^{+}

reduction half

Mn^{3+}(+3)\rightarrow Mn^{2+}(+2)

 balancing the reduction half by adding 1e^{-} on LHS side  

Mn^{3+}+1e^{-}\rightarrow Mn^{2+}

Add both balanced reduction half and oxidation half

2Mn^{3+}+2H_{2}O\rightarrow Mn^{2+}+MnO_{2}+4H^{+}

Posted by

Gautam harsolia

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