Then it is a mistake in the source I read this. Now, in my book there are some very simple examples, to calculate the EMF for Mg/Zn, Cu/Pb... cells. In these problems all the metals are equivalent so I didn't have trouble to do it, but in the problems, like the one I posted, it is more difficult for me to understand how to calculate it and to differentiate it from the electrode potential. I thank you for the help you gave me , it would be probably too much to ask from you, but:
Do you maybe know a good site where those more complex problems are correctly and more deeply explained?