Need for bubbling hydrogen gas as part of hydrogen electrode


> 
> Why the hydrogen gas should be bubbled continuously through the electrolyte in a hydrogen electrode? 
> 
> 
> 1. To keep the solution saturated with hydrogen gas
> 2. To clear the platinum electrode
> 3. To gate the highest electrode potential
> 4. To minimize loss of current
> 5. To speed up the process
> 6. To minimize the cost
> 
> 
> 


In my opinion:


1. This is false because the solution doesn't need to be saturated.
2. Maybe true because if the platinum electrode is full with hydrogen gas which isn't bubbled continuously, there will not be enough space on platinum electrode to let another $\ce{H2}$ gas dissociate.
3. This is false because it doesn't relate.
4. Maybe true because if the hydrogen gas isn't bubbled continuously, $\ce{H2}$ will not dissociate continuously and will not transfer electrons. So there will be lack of current through this electric cell.
5. Maybe true because if there's lack of current, it means that the process is too slow.
6. False because this choice doesn't relate.


But the question asks to choose just one choice. What choice is the best? Do my reasons for each choice make sense?




The hydrogen gas is the reactant of the half reaction, so it has to be present:


$$\ce{H2(g) ->[Pt(s)] 2H+(aq) + 2e-}$$


The platinum electrode is the catalyst, and water is the solvent or proton acceptor for the hydrogen ions that are generated. Once the hydrogen adsorbed on the platinum surface is depleted, the half reaction stops unless you supply more hydrogen gas.


In a standard hydrogen electrode, the pressure of the hydrogen gas is important because the voltage measured will depend on the pressure.


I am glad I don’t have to answer the multiple choice question posted by the OP. None of the answers seem appropriate.


 1

Hydrogen gas must be bubbled into the solution so that it is able to oxidize by losing electrons which they can't just in air. Platinum electrode need not be cleaned. Potential depends upon concentration of hydrogen, by "Nernst" equation. If hydrogen was there or not, current can never be lost, speed of process is kinetics and in no way related to thermodynamics. Cost, rubbish.


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