# Gas Electrode Working

How does a SHE electrode work?

Does the $H_2$ gas get absorbed on the platinum electrode? How is it reduced? How are electrons transferred from the adsorbed gas to the solution? How is $H^+$ liberated or how does the $H^+$ in the solution take electrons from the adsorbed $H_2$?

If platinum doesn't adsorb the $H_2$ gas, what is its use? How does it provide a surface for reduction/oxidation of hydrogen?

Also in a concentration cell, why is it, in evaluating Q(reaction quotient) you take pressure of a gas numerically and put it directly as a concentration?

And in evaluating log(Q) in nernst equation, Q isn't always unitless. But inside log, you can put only a unitless number, isn't that so?

And in concentration cells, if [c1] > [c2], then c1 acts as cathode. In Gases, considering Pressure=k[C], where k is a constant fixed at a particular temperature. then in gas concentration cell opposite happens if pressure 1 > pressure 2 then pressure 1 part acts as anode.

What is P? is it pressure of the gas above the solution?

In net, how does a gas electrode work?

• Welcome to Chemistry SE! Your question happens to be made up of a lot of smaller questions. Try asking each question separately instead of putting it all into one question. That makes it much clearer and much easier for us to answer. – kaliaden Apr 16 '13 at 14:38

The electrode is one half of an electrochemical circuit. The other half cell determines whether the SHE will behave as the cathode or the anode. If it is the anode, the electron flow comes from the external system to the platinum contact. 2 electrons reduce 2 acidic hydrogens from the solution to form one molecule of hydrogen, as in $2H^+ + 2e^- → H_2$. The molecular hydrogen then bubbles up above the solution. If the electrode is cathodic, hydrogen gas is absorbed on the platinum contact plate and oxidized to two acidic hydrogens which remain in solution. The electrons then flow to the external circuit. Electrons do not flow from hydrogen gas to the acid, or vice versa.