[CharlieCakeEater]

So its, been a while since I've done any real chemistry. What with me being a biology student and all. I was hoping someone could help me out?

So we were carrying out an experiment that looked at the effect on emf (and thus Eh) on the Ferri/Ferrocyanide system via the addition of NaCl.

Essentially I had equal amounts of ferricyanide and ferrocyanide and for some reason when NaCl was added the emf became more positive and I'm really not sure as to why this is the case. Could someone enlighten me or perhaps point me in the direction of a useful textbook that would explain the matter?

Cheers!

[Borek]

Try to estimate if it not just change in the ionic strength of the solution.

[CharlieCakeEater]

The thing is, I'm not sure why changing the strength of the solution like that would actually affect my mV readings when I'm adding Na+Cl- in equal volumes?

Is that something that should be affected, and if so why?

[Borek]

Ionic strength (not just strength) changes activity coefficients depending on ion charges, the higher the ion charge, the larger the change.

Google for Debye-Hückel theory.