दिये हुए सेल के लिए,
`E_(O.P._(M//M^(n+)))^(@)=E_(O.P._(M//M^(n+)))^(@)-(0.059)/(n)"log"[M^(n+)]`
`=+0.76-(0.059)/(n)"log"[0.002]` . . .(1)
`E_(R.P._(H^(+)//H))=E_(O.P._(H^(+)//H))^(@)+(0.059)/(1)"log"([H^(+)])/([P_(H_(2))]^(1//2))`
`=0+(0.059)/(1)"log"(1)/([1]^(1//2))=0` . . .(2)
समीo (1) तथा (2) से,
`:." "E_("cell")=E_(O.P._(M//M^(n+)))+E_(R.P._(H^(+)//H))`
`=0.76-(0.059)/(n)"log"[0.002]+0`
या `0.81=0.76-(0.059)/(n)"log"2xx10^(-3)rArrn=2`
अतः आयन `M^(2+)` है