Standard oxidation potential of `Ni|Ni^(2+)` electrode is 0.236V. If it is combined with a hydrogen electrode in acid solution, at what pH of the solution will the measured EMF be zero at `25^(@)C`? Assume `[Ni^(2+)]=1M and p(H_(2))=1atm.`

Explanation

`{:(" "Ni" "rarr" "Ni^(2+)+2e," "E_("Ox")^(@)=0.236V),(2H^(+)+2e" "rarr" "H_(2)," "E_("Red")^(@)=0),(_),(Ni+2H^(+)" "rarr" "Ni^(2+)+H_(2)," "E_("cell")^(@)=0.236V):}`
`E_("cell")=E_("cell")^(@)-(0.059)/(2)log.([Ni^(2+)])/([H^(+)]^(2))."At "25^(@)C, E_("cell")=0`,
`therefore" "E_("cell")^(@)=-(0.059)/(2)log.([H^(+)])/([Ni^(2+)])[Ni^(2+)=1]`
`"or, "0.236=-0.59log[H^(+)]or, -log[H^(+)]=4" "therefore pH=4`