What does a pH scale measure?

1 Answer
Sep 25, 2016

Answer:

It measures #[H_3O^+]#, i.e. hydronium ion concentration.

Explanation:

And #pH=-log_10[H_3O^+]#

#[H_3O^+]# derives from water's autoprotolysis:

#2H_2O(l) rightleftharpoonsH_3O^+ + HO^-#

At #298K#, #K_a=10^-14#, and thus #pH+pOH=14#