Question

A hydrogen electrode is immersed in a solution with
pH = 0 (HCl). By how much will the potential (reduction)
change if an equivalent amount of NaOH is added to the
solution. (Take pH₂ = 1 atm), T = 298 K.
(a) increase by 0.41 V (b) increase by 59 mV
(c) decrease by 0.41 V (d) decrease by 59 mV

Answer 1

The potential decreases by 0.41 V.

Option (C) is correct.

Explanation:

On adding equivalent amount NaOH, the pH of the solution will become 7.

Since, pH of solution = −log[H + ]

So, [H+ ] changes from 10^ -  10-7

Applying Nernst equation:

E = E 0 +   0.059 / n log[H+ ]

E = E0  +   0.059 / 1 log 10  −7

E = E0 - 0.41

Thus the potential decreases by 0.41 V.