The standard oxidation potential of Ni/Ni2+(Ni2+=1M) electrode is 0.236V. If this is combined with a hydrogen electrode (PH2=1atm) in acid solution, the pH at which the measured e.m.f. of the solution will be zero at 25oC is:
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Solution
The standard reduction potential of hydrogen electrode will be 0.236. This will make the cell potential zero. Eel=E0el−0.0592nlogPH2[H+]2 0.236=0−0.05922log1[H+]2 log1[H+]2=7.9729 [H+]2=1.06×10−8 [H+]=1.03×10−4 pH=−log[H+]=−log1.03×10−4=4