Can an acid be diluted with water?

As easy as this question may sound, I had 3 people at work vehemently insist that water of pH 7.0 cannot alter the pH of anything! I work in a biology laboratory, so you'd think they'd understand pH. They all claim that if you start with a droplet of acid of pH 2, and you add a quadrillion gallons of water, the new pH of the quadrillion gallons would be 2.

I say that water of pH 7 will, if added to a solution, steadily bring that solution toward pH 7 as you keep adding it. I even tested it in the lab, and it worked just like i said.

Their "proof" was that they took a solution which is a buffer (resists pH change by neutralizing H+ and OH-) and they added a bunch of water to it. The pH didn't change. I explained that this is the nature of buffers, but they said it's true for any liquid.

Anyone have a response? If not, whatever, it's retardedly obvious I'm right

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RIP Shiloh - I'll never forget ya

I'm inclined to agree with you.

I could be mistaken but isn't pH by its very definition a measure of its interactivity with Hydrogen? that is you add acid to water and the acid reacts with the Hydrogen i.e. the bubbling and splashing.

And after its done you get salt and hydrogen and shit.

At the very least its counter-intuitive to say a solution of 2% acid 98% water has the same PH as the same volume of liquids thats 100% of the acid.

the answer is 42, or C

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I bet she'd know.

hydrochloric, sulfuric, and muriatic acid as far as I have bothered to research can all be diluted in water

http://www.jamestowndistributors.com/us ... atch_type=

now whether an acid can be completely diluted with water I am not completely sure.

I'm not even remotely a rookie in this field, I'm below rookie but I hope the following helps

that's my girlfriend TS, you leave her alone :p

I was browsing and thought I'd input some...was learning about this last quarter for like 4 weeks strait in detail.

pH=pka + log ([A-]/[HA]), so if you add something into a buffer of acid that is a base it will change more of the acid buffer into the base form (A-). A log(larger/smaller) = a larger number, so pH of the acid buffer will increase. In this case water is the base since it is accepting H+ from the acid, and more of the acid turns into the A- form.

Buffers are built to resist changes in pH, but water is not some magical solution that doesn't change from the A- to HA form.

In chemistry for 16 year olds we used Hydrochloric Acid a lot, it was given to us in 1.0 molar and 2.0 molar concentration in bottles, but it was always pH 3 or thereabouts. In chemistry for 17-18 year olds we used hydrochloric acid a lot too, it was given to us in 10 molar concentration in flasks, and was still the same pH as we used the year before. I beleive it was delivered to the school in 18 molar concentration.

Adding water to it does not change the pH, but it does dilute it, so that the concentration of acid within the solution is much less. Hydrochloric acid is -always- the same pH, but the concentration of it can vary wildly, maybe thats where your confusion lies. And of course, a really low concentration of a low pH acid, will at least appear to be almost neutral, because its likely >90% water anyway.

I think in your argument you are both technically right, the pH of the acid itself is unchanged, it is still 3. But because by adding so much water to it, the solution is made up effectivly 100% water, it will have the pH of water, i.e 7.


Man I miss chemistry

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i think i disagree with "HCl is always the same pH"
that makes it sound like pH is an inherent property of any HCl
HCl has a pH of 0.1 only when it is at a concentration of 1M (1 molar, which is 1 mole per liter)

the inherent property you might be thinking of is pKa, the dissociation constant, which is a ratio of [H+][A-]/[HA] or dissociated vs associated

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RIP Shiloh - I'll never forget ya

[url=http://www.jtbaker.com/msds/englishhtml/H3880.htm]pH:
For HCL solutions: 0.1 (1.0 N), 1.1 (0.1 N), 2.02 (0.01 N) [/url]
from this i gather that when you dilute the HCl, you raise the pH, just like what happened in lab

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RIP Shiloh - I'll never forget ya

i was always taught you raise the overall pH of the solution it is in, and the amount of HCl is always the same pH, but it just has less and less effect on the overall pH of your solution as you add more water. Although you are more likely correct, I don't remember the dissociation constant at all.

Hmmm looking into a bit I think my answer before is wrong because I thought pH was a property of the acid, but really is a property of the solution. Oh well, if you accept that I think what I said still makes sense, and your colleagues who presumably have higher qualifications than a B at A-level chemistry should know better too

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Hey i've got a good idea, why don't you ask your biology lab buddies, being the geniuses they are, if you put a drop of acid into a lake would the entire lake be the pH of that acid drop? Because fish love acid lakes.

i got my biochemistry professor involved, and she said all my points are correct. my labmates also admitted they were unsure / wrong. they seemed so confident the day before...

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RIP Shiloh - I'll never forget ya

I hear dropping your starbursts into a glass jar of it and then reaching in with your hand to grab it helps reduce the pH.

Oh, and you're right, Whisp. As long as the liquids mix together and don't just form layers (think oil and water), then you could consider it to be diluted.

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haha

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RIP Shiloh - I'll never forget ya