Is ion activity in a salt solution pH-dependent? :) Without being a chemist myself, I need some basic understanding of the ion activities in my buffer solutions. 

Now I am wondering whether the ion activity of the K$^+$ and Cl$^-$ ions is different for the buffers with different pH-values.

When I google for that, all I get is ion activity for the hydrogen ion, which -I think- does not interest me at all.

If the ion activity actually IS different, could you point me to some table to look up the correction values?

Thank you!

.

edit: tl&amp;dr:  

The buffer solutions contain:
Buffer A: 250mM KCl, 10mM MOPS
Buffer B: 020mM KCl, 10mM MOPS  

pH is set to 5,6,7 resp., using unknown amounts of Tris.  

Is the ion activity of K$^+$ and Cl$^-$ affected by the pH?
Considering the effect of $\text{pH}$ on ion activity, one should take into account that $\ce{K+}$ and $\ce{Cl-}$ are respectively conjugated acid of a strong base and conjugated base of a strong acid. They are therefore both weak, with no influence on the $\text{pH}$. 

As a consequence, I would basically assume that also the other way round is true and that $\text{pH}$ has no effect on their activity.