Five ideas in chemical education that must die: pH 7 is neutral

By Eric Scerri2015-07-15T11:00:00

Source: Getty Images

Eric Scerri takes on the idea that pH 7 and neutral always coincide, and explains why it doesn't necessarily tell the whole story

The notion that pH 7 is always neutral and that neutral is always pH 7 is prevalent in the classroom, especially when the subject is treated qualitatively. But once the concept of K_w and its value of 10⁻¹⁴ is introduced, it becomes problematic. The problem is the notion that having a pH of 7 is both necessary and sufficient for neutrality to occur. In fact, it is neither necessary nor sufficient for a solution to be pH 7 for it to be neutral.

Inspired by the book This Idea Must Die Eric Scerri explores outdated chemical concepts, starting with the idea that pH 7 is neutral.

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