Question

For each given [H3O+] or [OH-], find the corresponding [OH-] or [H3O+] at 25°C.

Answer 1

Answer:

a) [H3O+] = 1.00 E-10 M ⇒ [OH-] = 1.0 E-4 M

b) [H3O+] = 1.00 E-4 M ⇒ [OH-] = 1.0 E-10 M

c) [H3O+] = 9.90 E-6 M ⇒ [OH-] = 1.0 E-9 M

Explanation:

• 14 = pH + pOH
• pH = - Log [H3O+]

a) [H3O+] = 1.00 E-10 M

⇒ pH = - Log(1.00 E-10) = 10

⇒ pOH = 14 - 10 = 4

⇒ 4 = - Log[OH-]

⇒ [OH-] = 1.0 E-4 M

b) [H3O+] = 1.00 E-4 M

⇒ pH = 4

⇒ pOH = 10

⇒ [OH-] = 1.0 E-10 M

c) [H3O+] = 9.90 E-6 M

⇒ pH = 5

⇒ pOH = 9

⇒ [OH-] = 1.0 E-9 M