But: solution has one potential only. If there are several redox pairs with different potentials substances will react till they get to equilibrium.
I am asking because what will be measured with the electrode is the water in closed circulation system.
But - I think that during process of the calibration the air oxygen will increase measured potential.
I know that for calibration people are using K4
] / K3
] solution (somewhat resistant to the air ?), but I want to use that what I have (Cu2+
/ Cu for example).
Any hints how to calculate what part of the potential (Cu2+
/ Cu) comes from the air oxygen ?
pH electrode doesn't measure potential related to the H+/H2 reaction. It measures potential related to the reaction of adsoprtion of H+ on the glass electrode surface (note: it is not a redox pair). This is not the same potential you will observe when you put Pt wire in the same solution.
But isn't true that SHE is the platinum electrode placed in the 1 M HCl solution under 1 atm H2
is present in water we drink and air we breathe (less than 1x10-7
M and 5 x 10-5
atm) - so IN THEORY - this should lower result of the potential.
In practice - I think that platinum electrode is not sensitive to H+
as the glass electrode, so won't be affected by that low H+