1.

E_(1),E_(2) and E_(3) are the emfsof the following three galvanic cells respectively. (i)Zn_((s))|Zn^(2+)(0.1M)||Cu^(2+)(1M)|Cu_((s)) (ii)Zn_((s))|Zn^(2+)(1M)||Cu^(2+)(1M)|Cu_((s)) (iii)Zn_((s))|Zn^(2+)(1M)||Cu^(2+)(0.1M)|Cu_((s)) Which one of the following is true?

Answer»

`E_(2)gtE_(1)gtE_(3)`
`E_(1)gtE_(2)gtE_(3)`
`E_(3)gtE_(1)gtE_(2)`
`E_(3)gtE_(2)gtE_(1)`

Solution :`E_(cell)=E_("OX")+E_(red)-(0.591)/(n)log[(Zn^(2+))/(Cu^(2+))]`
`E_(red)^(@)` for `Cu^(2)//Cu=0.35V`
`E_("ox")^(@)` for `Zn//Zn^(2+)`=0.76 V
`THEREFORE E_(cell)^(@)=E_(red)^(@)+E_("ox")^(@)=0.35+0.76=1.11V`
`Zn_(s)|Zn^(2+)(0.1M)|Cu^(2+)(1M)|CU_(s)`,`E_(1)`
`E_(cell)=E_(cell)^(@)-(0.0591)/(n)log[(Zn^(2+))/(Cu^(2+))]`
`=1.11-(0.591)/(2)log(0.1)/(1)=1.11+(0.591)/(2)toE_(1)`
(ii)For`Zn_(s)|Zn^(2+)(1M)|Cu^(2+)(1M)|Cu_(s)`
`E_(cell)=1.11-(0.591)/(2)log(1)/(1)`
`E_(cell)=1.11toE_(2)`
(III)Fo`Zn_(s)|Zn^(2+)(1M)||Cu^(2+)(1M)|Cu_(s)`
`E_(cell)=1.11-(0.0591)/(2)log(1)/(0.1)=1.11-(0.0591)/(2)toE_(3)`
`therefore E_(1)gtE_(2)gtE_(3)`.


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