Understanding ORP in Water with NaCl

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SUMMARY

This discussion focuses on the oxidation-reduction potential (ORP) of water when sodium chloride (NaCl) is dissolved in it. The user describes a scenario where 1 gram of NaCl is added to 1 liter of pure water, resulting in a solution with a pH of 9 and an ORP of -300 mV. The conversation highlights the importance of the Nernst equation in determining the redox potential, which is influenced by the pH and the partial pressure of oxygen in the solution. The participants clarify that the presence of NaCl does not automatically raise the pH to 9 without additional factors.

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  • Understanding of redox chemistry and oxidation-reduction potential
  • Familiarity with the Nernst equation and its application
  • Basic knowledge of pH and its measurement in aqueous solutions
  • Knowledge of the behavior of electrolytes like NaCl in water
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  • Explore the effects of different electrolytes on pH and ORP in water
  • Study the relationship between pH, ORP, and dissolved oxygen in water systems
  • Investigate the operation and chemistry of water ionizer machines
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Stephanus
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Dear PF Forum,
I would like to thank this forum for providing me invaluable helps lately. I'd like to understand ORP in water.
I'm aware that PF discourages member for not doing research first. I've (been) reading redox, antioxidant, pH, covalent, including: https://en.wikipedia.org/wiki/Reduction_potential and http://chemwiki.ucdavis.edu/Analyti.../Redox_Chemistry/Standard_Reduction_Potential
Frankly, I have no idea how ORP works.

So, perhaps I should give a condition first.
There are 1 liter pure H2O, 55.50622 moles.
In it I disolve 1 gr NaCl, 0.017112 moles. So that the water can be electrolyzed.
Now, as you know there are many water ionizer machines out there. Supposed I pump this solution to the machine, so that the water is divided by 2.
500 ml of it has PH = 9 and ORP = -300.
A: PH = 9 means that in this 500 ml of water there are 0.5 * 10-9 moles of H+, about 0.5 nanogram and 0.5 * 10-5 OH-, about 0.45 miligram. Is this true?
B: What about ORP. What element can make this water has ORP -300 milivolt?
Since I only use H2O and NaCl, I think there are some possible answers here:
H+, OH-, Na+, Na (neutral), HCl, anything?

Thank you very much.
 
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Stephanus said:
There are 1 liter pure H2O, 55.50622 moles.
In it I disolve 1 gr NaCl, 0.017112 moles. So that the water can be electrolyzed.
Now, as you know there are many water ionizer machines out there. Supposed I pump this solution to the machine, so that the water is divided by 2.
500 ml of it has PH = 9 and ORP = -300.

When you dissolve NaCl in water the solution is more or less just neutral, it doesn't become automagically pH 9 for no apparent reason.

As far as I am aware in normal conditions redox potential you can measure after putting an electrode in water would be that of O2/OH- system (where O2 comes from the atmosphere). The exact potential will depend on the pH and partial pressure of oxygen and it will be given by the Nernst equation.
 
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