pH values

[Sophia Tate 1L]

In class, we talked about how when [H30+] is less than 10^-7, then the solution is considered neutral because we know autoprotolysis generates 10^-7 mol/L [H3O+]. When would we apply this in a problem? Would it be when calculating the pH of a weak acid? Thanks!

[Chem_Mod]

Hi!

You can use the fact that [H3O+] = 10^-7 for pure water at 25 degrees celsius. You'll most likely use the fact that Kw = 10^-14 = [H30+][OH-] or pH + pOH = 14 AT 25 DEGREES CELSIUS in your problems, when calculating pH or concentrations of certain ions at equilibrium. However, you could use the fact that [H3O+] = 10^-7 for pure water (neutral solution) as a qualitative fact check.

Hope this is helpful!