Standard Electrodes: Pressure & Half Cell Potential Impact

[ajayguhan]

In standard electrodes, why it is necessary to maintain the pressure as 1 atmosphere, is the potential of an half cell depends on pressure too? If yes then how the potential of an half cell depends upon pressure?

Say for example, i know that in standard hydrogen electrodes we maintain the concentration and temperature as 1M and temperature 25°C since the potential depends upon temperature and concentration of the electrolyte.but why should we maintain the pressure as and1 atmosphere? If the potential depends upon pressure, how come they are related i didn't get the logic!

 

[Borek]

Note that the concentration of the dissolved gaseous hydrogen is directly proportional to the pressure of the gas over the solution (even heard about Henry's law?). But dealing with the concentration is inconvenient, it is easier to express the gas presence using its pressure. And just like we assume 1M solution is the standard state for an ion, we assume 1 atm is a standard state for the gas.