Molarity of hydrogen gas in standard hydrogen electrode I am unable to understand the folowing statement of Wikipedia it is about standard hydrogen electrode :


  The concentration of both the reduced form and oxidised form is maintained at unity. That implies that the pressure of hydrogen gas is 1 bar. 


But why if I apply ideal gas equation then I am getting molarity of nearly 0.004M .this is condradiction to the statement in Wikipedia. N/V=P/RT THEREFORE M=N/V~0.004
The standard hydrogen electrode is a "reference electrode." It is supposed to be used with ultra-low currents. 

In operation, hydrogen gas is bubbled through a 1 N acid solution, but there is little hydrogen gas in the solution. In order to get the hydrogen gas to bubble through the solution, a pressure of a bit more than 1 bar must be used.