1.

Two half-reactions of an electrochemical cell are given below : `MnO_(4)^(-)(aq)+8H^(+)(aq)+5e^(-) toMn^(2+)(aq)+4H_(2)O(l), E^(@)=+1.51" V"` `Sn^(2+)(aq) to Sn^(4+)(aq)+2e^(-),E^(@)=-0.15" V"`

Answer» Multiply the first equation by 2 and second equation by 5. Add up these equations.
`2MnO_(4)^(-)(aq)+16H^(+)(aq)+10e^(-) to 2Mn^(2+)(aq)+8H_(2)O(l),E_(cell)^(@)=+1.51" V"`
`(5Sn^(2+)(aq) to 5Sn^(4)(aq)+10e^(-),E^(@)=-0.15" V")/(2MnO_(4)^(-)(aq)+16H^(+)(aq)+5Sn^(2+)(aq) to 2Mn^(2+)(aq)+5Sn^(4+)(aq)+8H_(2)O(l))`
`E^(@)=(1.51-0.15)=1.36" V"`
Since `E_(cell)^(@)` comes out to be positive, the reaction is reactant favoured. It is likely to proceed in the backward direction.


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