pH Scale is broken?

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Frederick Keith_4C
Posts: 65
Joined: Thu Sep 26, 2019 12:19 am

pH Scale is broken?

Postby Frederick Keith_4C » Sun Dec 01, 2019 11:39 am

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?

Julie Park 1G
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

Re: pH Scale is broken?

Postby Julie Park 1G » Sun Dec 01, 2019 12:26 pm

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.

Robert Tran 1B
Posts: 118
Joined: Thu Jul 11, 2019 12:15 am

Re: pH Scale is broken?

Postby Robert Tran 1B » Sun Dec 01, 2019 12:42 pm

pH values are not solely confined to the values 0-14. However, most solutions fall within this range.

ZevMarx-Kahn3C
Posts: 52
Joined: Sat Aug 17, 2019 12:17 am

Re: pH Scale is broken?

Postby ZevMarx-Kahn3C » Sun Dec 01, 2019 3:26 pm

Are there any examples we should know of that fall outside the 0-14 range?

Alex Chen 2L
Posts: 86
Joined: Wed Sep 18, 2019 12:21 am

Re: pH Scale is broken?

Postby Alex Chen 2L » Sun Dec 01, 2019 4:07 pm

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).

Tiffany Dong_4e
Posts: 51
Joined: Wed Sep 11, 2019 12:17 am

Re: pH Scale is broken?

Postby Tiffany Dong_4e » Sun Dec 01, 2019 4:14 pm

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.

pauline young 1L
Posts: 50
Joined: Thu Jul 11, 2019 12:15 am

Re: pH Scale is broken?

Postby pauline young 1L » Sun Dec 01, 2019 4:17 pm

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.


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