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Old Dec 19th 2014, 08:10 PM   #1
jrip
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Question pH dilution problem

Im trying to programmatically simulate the dilution of a liquid with a given pH, and determine the resulting pH. The problem I'm running into is that nothing in the equation results in the the new pH approaching (but not reaching/crossing) 7.

Given that
pH1 = 6.8
m1*v1 = m2*v2,
m = 10 ^ -pH,

m1 = 10 ^ -6.8
m1 = 1.5848931924611 * 10^-7
m2 = (m1 * v1) / v2
m2 = (1.5848931924611 * 10^-7 * 0.40) / 1
m2 = 6.3395727698445 * 10^-8
ph2 = -1*log10(6.3395727698445 * 10^-8)
ph2 = 7.197940008672


As I understand it, the pH should never dilute beyond 7, since we're simply adding water, with a pH of 7. What fundamental thing am I missing that would make this make sense?
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Old Dec 20th 2014, 10:41 AM   #2
bjhopper
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pH dilution problem

pH = - log (H^+) where the (H^+) is the hydrogen ion conc in molesper liter
pH =6.8 10^6.8=1/(H^+) (H^+) =1.58x10^-7 mols/liter
distilled water (H^+ ) = 1x10^-7 mols /liter
when the water is added the new conc of(H^+) will define the new pH between 6.8 and 7.0
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