Question

Calculate the [H+] and [OH-] in each of the following aqueous solutions.
solution
          [H+]            [OH-]          acidic/basic
a) pH = 9.21
b) pOH = 14
c) pH = 11.58
d) pOH = 8.37
e) pH = 9.33
f) pH = 6.04

Answer 1

	[H]+	[OH-]
(a)	6.17 x 10-10 M	1.62 x 10-5 M Basic
(b)	1 M acidic	1.0 x 10-14 M
(c)	2.63 x 10-12 M	3.80 x 10-3 Basic
(d)	2.34 x 10-6 M Acidic	4.27 x 10-9 M
(e)	4.68x 10-10 M	2.14 x 10-5 M Basic
(f)	9.12 x 10-7 M Acidic	1.09 x 10-8 M

This problem requires calculation of hydrogen and hydroxide ion concentrations. Given the pH or pOH you can calculate these directly. The equation is as follows: pH=-log₁₀[H⁺] and pOH=-log₁₀[OH^-]. pH + pOH=14. Also a concept of the ion product constant of water must be introduced. The concentration of hydroxide ions and hydrogen ions, when multiplied together equal this number: 1.0 x 10^-14 M. So if you find either of the numbers, you can easily solve for the other. Also, if [H+] > [OH-] then the solution is acidic, and vice versa. Hope this helps. Comment if you have questions.