I am an industrial electrician apprentice who needs to learn more about pH-measurements and how the temperature effects the measurement itself (I am in charge of all the pH measurements on the powerplant I work at and I have no one to ask about this stuff as no one knows a thing about pH measurements).
So far I have learned how the temperature affects the electrochemical and physical properties of the combination electrode and how this can easily by adjusted for by incorporating an automatic temperature compensation that keeps the NERNST equation updated in real time.
So far so good.
I have, however, also read about the auto-ionisation of water and the constant pKw and how a change in temperature affects the span of the pH scale: With a change in temperature comes a change in hydronium content due to a shift in equilibrium as predicted by Le Chatelier's Principle. However, with a change in hydronium content comes an equal change in hydroxide content and so a change in this constant DOES NOT change the acidity of a solution. In other words, this particular constant decides the SPAN of the pH scale and because of this also the point of neutrality (7 at 25 degree celcius in pure water and less at higher temperatures).
And then there is the so called pKa that says something about the strength of an acid via the acids point of equilibrium in water. This dissociation constant is also temperature dependent although it is my understanding that this constant have nothing to do with the location of the neutrality point. It's simply a constant that changes with temperature and so the solution (unlike with pKw) DOES become more/less acidic as the temperature changes.
Is this correct?
If so, could you please give me an answer to the following questions I have?
Why does a solution become less temperature dependent the more acidic it is? Basic solutions are extremely temperature sensitive, neutral solution still significant sensitive, but highly acidic solutions don't seem give a damn about temperature. Why is that?
It is my understanding that pKw is only important in pure water and highly diluted solutions. But what am I to make about this? If I have a tank of an acidic solution (say pH 1) and the temperature is 50 degrees celcius, does this mean that the point of neutrality hasn't shifted as much away from pH 7 as it would had done in pure water? Or is it because there is simply so much hydronium present that the pKa constant takes up proportionally more importance than pKw and so the autoionisation becomes a non issue to consider in every practical sense?
Thanks in advance for any help you may provide me with