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Topic: pH and Dilution  (Read 7482 times)

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Offline kaynable

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pH and Dilution
« on: May 25, 2009, 07:18:46 PM »
What would be the best formula or method for solving this?
How much H2O of pH 7.4 is required to dilute 15,000 cubic L of 30% HCL to a pH of 7.3?
Thanks ahead for any input
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Offline Borek

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Re: pH and Dilution
« Reply #1 on: May 26, 2009, 03:04:44 AM »
This is very bad question. It is not about dilution, but about neutralization of some unknown substance - pure water doesn't have pH of 7.4. Not knowing what the substance is, it is impossible to calculate the answer.

You may calculate the answer from simple stoichiometry, assuming that your water was a solution of a strong base. You will need to account for concentrated HCl density.
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Offline AWK

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Re: pH and Dilution
« Reply #2 on: May 26, 2009, 05:01:59 AM »
Pure water has pH about 7.4 at temperature about 2 C.
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Offline Borek

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Re: pH and Dilution
« Reply #3 on: May 26, 2009, 05:10:49 AM »
Quote from: AWK on May 26, 2009, 05:01:59 AM
Pure water has pH about 7.4 at temperature about 2 C.

Good point, but I doubt it was the idea behind :)
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Offline kaynable

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Re: pH and Dilution
« Reply #4 on: May 26, 2009, 08:59:42 AM »
Haha, well if it's any help to my question:

It has a pressure of 43 mPa, the temp would be about 100C.  The water is actually saturated in KCl.  The base is unknown, but it would be a weak base.
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Offline Borek

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Re: pH and Dilution
« Reply #5 on: May 26, 2009, 09:34:18 AM »
If it is a weak base, there is no answer to the question without information about base concentration and pKb.
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