Question

What is the reaction that takes place at the standard hydrogen electrode if it's coupled with metal-metal ion electrode of zinc (zinc in zinc sulphate solution).

• A. $Pt\to P{t}^{+}+e^{-}$
• B. $P{t}^{+}+e^{-}\to Pt$
• C. $H_2\to 2H^{+}+2e^{-}$
• D. $2H^{+}+2e^{-}\to H_2$

Answer 1

The correct option is D $2H^{+}+2e^{-}\to H_2$

For standard hydrogen electrode
$E_{H^{+}(aq.)|\frac{1}{2}{H}_2\left(g\right)}^{-}$= 0 volt

For metal metal ion electrode
$E_{Z{n}^{2+}(aq.)|Zn\left(s\right)}^{-}$ = -0.76 volt.

Hydrogen Electrode has more postive reduction potential thus it acts as the cathode where reduction of $H^{+}$ occurs as
$2H^{+}+2e^{-}\to H_2$