Correlation between pH and cation/anion imbalance?

[Silver_Is_Money]

If all deviation in cation/anion imbalance due to analytical error was to be eliminated, would some very small degree of charge imbalance still exist as a manifestation of water pH? Is there any such imbalance correlation?

 

[ajdelange]

No. Natural water is neutrally charged (unless you bring it into the vicinity of a Van de Graff gernerator or do something similar). The charge on water at some pH is 10^-pH - 10^(pH - 14) Eq/L. Thus if the pH is less than 7 the charge on water will be positive and conversely. But how would we get the pH to be less than 7? Add an acid, such as HCl, of course. Say we added enough acid to get the pH to 4. This implies a positive charge of + 10^-4 Eq/L. But as the solution is neutral there must be 10^-4 Eq/L negative charges in the water as well. These are, of course, supplied by the chloride ions from the HCl we added.

 

[Silver_Is_Money]

No. Natural water is neutrally charged (unless you bring it into the vicinity of a Van de Graff gernerator or do something similar). The charge on water at some pH is 10^-pH - 10^(pH - 14) Eq/L. Thus if the pH is less than 7 the charge on water will be positive and conversely. But how would we get the pH to be less than 7? Add an acid, such as HCl, of course. Say we added enough acid to get the pH to 4. This implies a positive charge of + 10^-4 Eq/L. But as the solution is neutral there must be 10^-4 Eq/L negative charges in the water as well. These are, of course, supplied by the chloride ions from the HCl we added.

Thanks A.J.! As I understand this from your explanation, water is to be considered neutrally charged regardless of its mineralization level or its pH.

Prior to your explanation I was wondering if some percentage of the cation/anion imbalance inevitably seen within (for example) a Ward Labs report was due to the pH, but now I know it is 100% due to analytical variance from actual.