2006-06-20 07:03:06 · 10 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
The pH of distilled water that is kept out of contact with the atmosphere should be approximately 7 (the actual pH depends on temperature).
If the water is exposed to air, carbon dioxide (CO2) in the air will dissolve in the water (and you, in fact, no longer have distilled water). When this happens, the CO2 reacts with water to form carbonic acid:
CO2(g) + H2O (liquid) <-> H2CO3(aq)
Carbonic acid is a weak diprotic acid that dissociates into hydrogen ions, bicarbonate ions, and carbonate ions. The presence of hydrogen ions is what makes the solution slightly acidic. At 25 C, the pH of a water (with no other solutes) in equilibrium with air containing ~350 ppm CO2 should be about 5.65.
H2CO3(aq) <-> HCO3- + H+
HCO3- <-> CO3-- + H+
2006-06-20 07:35:41 · answer #1 · answered by hfshaw 7 · 2⤊ 1⤋
Usually distilled water has dissolved gas contaminants in it (mostly carbon monoxide). Because distilled water has almost no mineral contaminants, it is completely unbuffered and a very little bit of CO2 makes enough carbonic acid to reduce the pH, often to as low as 5.5.
2016-03-26 22:57:37 · answer #2 · answered by Anonymous · 0⤊ 0⤋
hfshaw's answer is correct, I think. Carbon dioxide in air could be a major cause for low pH in distilled water.
WITHOUT contacting air, the pH value of distilled water will be 7.
2006-06-20 08:36:11 · answer #3 · answered by nickyTheKnight 3 · 0⤊ 1⤋
distilled water is or should be 4.5to 5.5 . 5.5 being more likely .
distilled water for sure is not or ever 7.0 sorry everyone.
Do I know why ? No
But I keep carnivorous plants for a hobby and I have tested this with strips and a digital meter on average distilled water is 5.5-4.5ish
2014-01-31 11:44:09 · answer #4 · answered by Russell 1 · 0⤊ 0⤋
ph changes due to change in temperature as ph shows the power of acid water is neither acid nor base but it changes due to change in temperature
2006-06-20 07:18:52 · answer #5 · answered by kashish s 1 · 0⤊ 0⤋
Possibly because you have carbon dioxide from the air dissolving in the water.
2006-06-20 08:21:32 · answer #6 · answered by Math_Guru 2 · 0⤊ 1⤋
It could be that without any minerals in it, it lacks the ability to "buffer" the carbon dioxide being dissolved into it through the air.
2006-06-20 07:08:48 · answer #7 · answered by squirespeaks 2 · 0⤊ 1⤋
depends on the meter and how the water was distilled. check instrumentation and then reevaluate.
2006-06-20 07:06:33 · answer #8 · answered by shiara_blade 6 · 0⤊ 1⤋
as much as i recon,it is 7 because pure distilled water is neither acidic neither basic(alkalic)
2006-06-20 12:21:02 · answer #9 · answered by tonima 4 · 0⤊ 1⤋
Should be 7 I think.
2006-06-20 07:05:16 · answer #10 · answered by kurticus1024 7 · 0⤊ 1⤋