Question

What is the pH of HCl solution when the hydrogen gas electrode shows a potential of −0.59 V at standard temperature and pressure?

Answer 1

Given, the potential of hydrogen gas electrode = −0.59 V

Electrode reaction: \[\ce{H^{+} + e^{-} -> 0.5 H2}\]

Applying the Nernst equation,

E(H⁺/H²) = E^o(H⁺/H₂) − `0.059/"n"  log  ([H_2]^(1/2))/([H^+])`

E^o(H⁺/H₂) = 0 V

E(H⁺/H₂) = −0.59 V

n = 1

[H₂] = 1 bar

−0.59 = 0 − 0.059 (− log [H⁺])

−0.59 = −0.059 pH

∴ pH = 10