Predict the products of electrolysis in each of the following
(i) an aqueous solution of `AgNO_(3)` with silver electrodes.
(ii). An aqueous solution of `AgNO_(3)` with platinum electrodes.
(iii). A dilute solution of `H_(2)SO_(4)` with platinum electrodes.
(iv). An aqueous solution of `CuCl_(2)` with platinum electrodes.

Answer

`a. `Cathode`:Ag, ` Anode `:Ag^(o+)`
`b.` Cathode `:Ag,` Anode`:O_(2)`
`c.` Cathode`:H_(2),` Anode`:O_(2)`
`d.` Cathode`:Cu` Anode`:Cl_(2)`

Explanation

`a.` An aqueous solution of `AgNO_(3)` with `Ag` electrode
`AgNO_(3) rarr Ag^(o+)=NO_(3)^(c-)`
`i.` Reduction potential of `Ag^(o+)gt` Reduction potential of `H_(2)O`.
So reduction of `Ag^(o+)` occurs to `Ag` at cathode.
At cathode `: Ag^(o+) +e^(-) rarr Ag`
`ii. ` Comparing oxidation potential of `NO_(3)^(c-),H_(2)O` and `Ag`, it is clear that the oxidation potential of `Ag` is highest.
So `Ag` from silver electrode will undergo oxidation at anode. ltbr. At anode `: Ag rarr Ag^(o+)+e^(-)`
This method is used for electrolytic refining of `Ag`. Impure `Ag` electrode is made anode and thin sheet of pure `Ag` is made cathode. Pure `Ag` from anode dissolves into the solution and gets deposited on pure `Ag` cathode. Impurities from impure `Ag` anode fall down as anode mud.
`b.` An aqueous solution of `AgNO_(3)` with platinum electrodes.
`i.` At cathode, same as in `(a)` above.
Since `Pt` is an inert electrode.
`ii.` Compare the oxidation potential of `NO_(3)^(c-)` and `H_(2)O` . The oxidation potential of `H_(2)Ogt` oxidation potential of `NO_(3)^(c-)` .
So the oxidation of `H_(2)O` occurs at anode .
At anode`:H_(2)O rarr 2H^(o+0+2e^(-) (1)/(2) O_(2)(g)`
`c.` `1.` A diulte solution of `H_(2)SO_(4)` with platinum electrodes.
`H_(2(SO_(4) rarr 2H^(o+)+SO_(4)^(2-)`
At cathode `:2H^(o+) +2e^(-) rarr H_(2)(g)`
`2.` Two reaction are possible at anode `: `
`1. H_(2)O(l) rarr 2H^(o+)+2e^(-)+(1)/(2)O_(2)(g)`
`2. 2SO_(4)^(2-)(aq) rarr S_(2)O_(8)^(2-)(aq)+2e^(-), E_(cell)^(c-)=1.96V`
For dilute `H_(2)SO_(4)`, reaction `(1)` is preferred but at higher concentration of `H_(2)SO_(4)`, reaction `(2)` is preferred and for `50%` aqueous `H_(2)SO_(4)`, both reaction `(1)` and `(2)` occur simultaneously.
`d.` An aqueous solution of `CuCl_(2)` with `Pt` electrodes
`i.` `CuCl_(2) rarr Cu^(2+) +2Cl^(c-)`
At cathode `:Cu^(2+)+2e^(-) rarr Cu(s)`
Since the reduction potential of `Cu^(2+)|Cugt` reduction potential of `H_(2)O`. So, reduction of `Cu^(2+)` to `Cu` occurs at cathode .
`ii.` At anode `:2Cl^(c-) rarr Cl_(2)(g)+2e^(-)`
Although the oxidation potential of `H_(2)Ogt` oxidation potential of `Cl^(c-)` .
But oxidation of `Cl^(c-)` to `Cl_(20` is preferred at anode on the account of overpotential of `O_(2).`
So `Cu` is deposited at cathode and `Cl_(2)(g)` is liberated at anode.