Question

The normal oxidation potential of zinc referred to the standard hydrogen electrode is 0.76 volt and that of copper is -0.34 volt at `25^(@)C`. When excess of zinc is added to a solution of copper sulphate the zinc displace copper till equilibrium is reached. What is the ratio of concentration of `Zn^(2+)` to `Cu^(2+)` ions at equilibrium ?

Answer 1

The reaction is,
`Zn + CuSO_(4) rarr Cu+ZnSO_(4)`
or `Zn+Cu^(2+) rarr Cu+Zn^(2+)`
`E_(cell)=E_(cell)^(@)-0.0591/2"log" ([Zn^(2+)])/([Cu^(2+)])`
At equilibrium, `E_(cell)=0`
`E_(cell)^(@)=0.0591/2"log"([Zn^(2+)])/([Cu^(2+)])`
or `"log"([Zn^(2+)])/([Cu^(2+)])=(2xxE_(cell)^(@))/(0.0591)`
`(E_(cell)^(@)=0.76+0.34=1.10" volt")`
`=(2xx1.10)/0.0591=37.225`
`([Zn^(2+)])/([Cu^(2+)])=1.679xx10^(37) : 1`