Question

What are the H3O+ and OH− concentrations of solutions that have the following pH values? 11, 1.34, 7.46

Answer 1

1) pH = 11

POH = 14 - pH
= 14 - 11
= 3

use:
pH = -log [H+]
11 = -log [H+]
[H+] = 1*10^-11 M

use:
pOH = -log [OH-]
3 = -log [OH-]
[OH-] = 1*10^-3 M


Answers:
[H3O+] = 1*10^-11
[OH-] = 1*10^-3

2) pH = 1.34

POH = 14 - pH
= 14 - 1.34
= 12.66

use:
pH = -log [H+]
1.34 = -log [H+]
[H+] = 4.571*10^-2 M

use:
pOH = -log [OH-]
12.66 = -log [OH-]
[OH-] = 2.188*10^-13 M


Answers:
[H3O+] = 4.571*10^-2
[OH-] = 2.188*10^-13

3) pH = 7.46

POH = 14 - pH
= 14 - 7.46
= 6.54

use:
pH = -log [H+]
7.46 = -log [H+]
[H+] = 3.467*10^-8 M

use:
pOH = -log [OH-]
6.54 = -log [OH-]
[OH-] = 2.884*10^-7 M


Answers:
[H3O+] = 3.467*10^-8
[OH-] = 2.884*10^-7