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pH Scale is broken?

Posted: Sun Dec 01, 2019 11:39 am
by Frederick Keith_4C
If the scale is 0-14, how come some acids and bases have pHs beyond the scale? Like how is it possible to get a negative pH or a pH above 14 if the scale is 0-14? Why don't we change the scale to accommodate those acids and bases?

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 12:26 pm
by Julie Park 1G
Since pH is found by using the equation -log(x), where x is the concentration of hydrogen ions, pH will be negative as long as the hydrogen ions have a molarity greater than 1 (due to the behavior of the -log function). Because a negative pH is really hard to calculate experimentally due to lack of well-calibrated instruments, negative pHs are generally not mentioned. There has been some debate about whether the pH scale should be "open-ended" in the sense where arrows pointing to the left of 0 and to the right of 14 should be incorporated, but I think that for simplicity-related reasons, the 0-14 scale is most often used.

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 12:42 pm
by Robert Tran 1B
pH values are not solely confined to the values 0-14. However, most solutions fall within this range.

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 3:26 pm
by ZevMarx-Kahn3C
Are there any examples we should know of that fall outside the 0-14 range?

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 4:07 pm
by Alex Chen 2L
ZevMarx-Kahn3C wrote:Are there any examples we should know of that fall outside the 0-14 range?


I don't think there are any specific examples we should know, since I looked some up and they all look complicated. Just know that they are called superacids if the pH is negative (below 0).

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 4:14 pm
by Tiffany Dong_4e
Superacids and superbases were briefly mentioned in class, but I believe we don't accommodate for them because they are extreme cases. For the most part, acids and bases should fall within the 0-14 pH scale.

Re: pH Scale is broken?

Posted: Sun Dec 01, 2019 4:17 pm
by pauline young 1L
i think knowing that there are acids and bases that go beyond the scale is enough, we don't need to specifically memorize any cases of that.