Log scale with pH of Acids and Bases

[Ashley Barrera 1J]

Hi, does anyone know why in the example from Jan 17th lecture the hydronium ion is 100 times higher on a log scale? I guess what I am asking is why is the hydronium acid 10 times greater and not the hydroxide base?

[Brian Phung 2B]

I believe in the first part, you mean the hydronium ion is 10x greater for each step down of the pH scale. This is because the pH scale is relative to hydronium ion concentration. For example a pH of 2 corresponds to 10^-2 M and 10^-1 corresponds to a pH of 2, and this concentration is 10x greater than 10^-2. With the hydroxide ion, the concentration would be 10 times lesse rfor each step done because pH measure H+ concentration and more h+ means less OH=, considering [H+][OH-] =10^-14

If this was a pOH scale the opposite would be true.