Is Charge Sum in Solutions a Complete Approximation?

AI Thread Summary
The discussion centers on whether the charge sum in solutions, specifically for a 0.10 M Na2SO4 solution, is a complete approximation. It highlights that the charge sum calculated from stoichiometry appears to be 0.20 but may overlook the auto-ionization of water, which produces hydronium and hydroxide ions. The participant questions if this oversight significantly impacts solution considerations, suggesting that ions in very small concentrations are often disregarded. The full charge balance equation is presented, emphasizing the relationship between sodium, sulfate, and the ions from water. Overall, the conversation explores the nuances of charge balance in ionic solutions.
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Homework Statement



Question: is the charge sum an approximation?

Homework Equations



E.g. consider 0.10 M Na_{2}SO_{4} solution.

Charge sum appears to be 0.20 from elementary stoichiometric considerations.

The Attempt at a Solution



The charge sum, however, seems to be ignoring the auto-ionization of water, which forms two ions - hydronium and hydroxide. Am I correct? This doesn't make a significant difference for most solution considerations, right?
 
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We often ignore ions present in very small concentrations, but full charge balance equation for sodium sulfate solution is

[Na^+] + [H^+] = 2[SO_4^{2-}] + [OH^-]
 
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