Calculate `E^(C-)` for each cell and write the equation for each cell precess. Explaing the significance of any negative. `E^(c-)` value.
`a.` `Cd(s)|Cd^(2+)(1.0M)||AgNO_(3)(1.0m)|Ag(s)`
b. `Fe(s)|FeSO_(4)(1.0M)||ZnSO_(4)(1.0m)|Zn(s)`
`c.` `Pt, Cl_(2)(g)(1 atm)|NaCl(1.0M)|Hg_(2)Cl_(2)(s)|Hg(s)`
Given `E^(c-)._(Cd)=-0.40V,E^(c-)._((Fe))=-0.41V,E^(c-)._((Zn))=-0.76V`
`E^(c-)._((Ag))=+0.80V,E^(c-)._((2Cl^(c-)|Cl))=-1.36V.`
`E^(c-)._((Hg|Hg_(2)Cl_(2)))`=-0.27V.`

Explanation

`a.` Anode `:" "Cd(s) rarr Cd^(2+)(1.0M)+ `cancel(2e^(-))`
Cathode `:`
`2Ag^(o+)(1.0M)+ `cancel(2e^(-))` rarr 2Ag(s)
Cell reaction `:`
`ul(bar(Cd(s)+2Ag^(o+)(1.0M)rarrCd^(2+)(1.0M)+2Ag(s)))`
`E^(c-)._(cell)=(E^(c-)._(reduction ))_(cathode)-(E^(c-)._(reduction))_(anode )`
`=0.80-(-0.4)=1.2V`
`EMF` of cell is positive, hence the cell will function with `Cd` as anoe and `A` as cathode.
`b.` Anode `: Fe(d) rarr Fe^(2+)(1.0M)+ cancel(2e^(-))`
Cathode`: Zn^(2+)(1.0M)+ cancel(2e^(-)) rarr Zn(s)`
Cell reaction `:`
`ulbar(Fe(s)+Zn^(2+)(1.0M)rarrFe^(2+)(1.0M)+Zn(s))`
`E^(c-)._(cell)=(E^(c-)._(reduction))_(cathode)-(E^(c-)._(reduction))_(anode)`
`=0.76-(-0.41)=-0.35V`.
Negative `EMF` valuse suggests that cell will not function in the manner it is represented , `i.e.,Fe` as anode and `Zn` as cathode. So reversing `(` interchanging `)` the cathode and anode, `i.e,` making `Zn` as anode and `Fe` as cathode, can make the cell functional.
`c.` Anode `: cancel(2Cl)(1.0M)rarrCl_(2)(1.0atm)+cancel(2e^(-))`
Cathode`:`
`Hg_(2)Cl_(2)(s)+cancel(2e^(-)) rarr 2Hg(s)+2Cl^(c-)(1.0M)`
Cell reaction `:`
`ulbar(Hg_(2)Cl_(2)(s)rarr 2Hg(s)=Cl_(2)(1.0atm))`
`E^(c-)._(cell)=(E^(c-)._(reduction))_(cathode )-(E^(c-)._(reduction))_(anode)`
`=0.27-(1.36)=-1.09V`
Negative `EMG` value suggests that the cell will note function in the manner it is represented, `i.e., HgCl_(2)` as cathode and `2Cl^(c-)|Cl_(2)` as anode. So reversing`(` interchanging `)` the cathode and anode, `i.e.,` making `Hg_(2)Cl_(2)( i.e., Hg|Hg_(2)Cl_(2))` as anode and `Cl_(2)|2Cl^(c-)` as cathode, can make the cell functional.