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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: tchristides on June 13, 2009, 05:56:28 PM

Title: pH deionized water
Post by: tchristides on June 13, 2009, 05:56:28 PM

Why is the pH of my double deionized water less than 7?  It's about 6.4.

Title: Re: pH deionized water
Post by: Borek on June 13, 2009, 06:07:47 PM

CO₂.

Title: Re: pH deionized water
Post by: Johnny010 on August 20, 2009, 07:32:03 AM

CO₂ dissolves and forms carbonic acid.
If the deionisation was done under strict inert atmosphere then the pH would have been 7.

http://209.85.229.132/search?q=cache:pNeRYArS0jEJ:www.thuisexperimenteren.nl/infopages/Carbondioxide%2520in%2520water%2520equilibrium.doc+solubility+of+CO2&cd=4&hl=en&ct=clnk&gl=uk&client=firefox-a

If you wish to read up about it. I think this goes into the whole Ka values and such.