A further relation essential to the description of electrolyte solutions - electrical neutrality

12 A further relation essential to the description of electrolyte solutions - electrical neutrality 

If each Na (aq) contributes one positive charge, then UNa+ mol firom the NaCl will contribute nNa+ mol of positive charge. Hence the total positive charge firom the NaCl(aq) will be proportional to the concentration, Na+ /volume of solution, i.e. [Na ]actuai- A similar argument will apply to the other positive charges and to the negative charges. 

Since the solution will have neutral pH, [H30+]actuai = [OH lactuai then 

When divalent ions are present this multiple charge on the ion must be included, e.g. Ba (aq) present in a solution will contribute two positive charges, and the total positive charge contributed will be 2[Ba ]actuai- Likewise if the P04 (aq) ion were present it would contribute 3[P04 ]actual of negative charge. For the redox reaction, given in Section 2.3, where the chloride salts are used  

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