Question

Solution X has a pH of 9.20, and solution Y has a pH of 8.4.

A.) What is the [H3O+] in solution X?

Express your answer to one significant figure and include the appropriate units.

B.) What is the [H3O+] in solution Y?

Express your answer to one significant figure and include the appropriate units.

C.) What is the [OH−] in solution X?

Express your answer to tone significant figure and include the appropriate units.

D.) What is the [OH−] in solution Y?

Express your answer to one significant figure and include the appropriate units.

Answer 1

A)

use:

pH = -log [H3O+]

9.2 = -log [H3O+]

[H3O+] = 6.31*10^-10 M

Answer: 6*10^-10 M

B)

use:

pH = -log [H3O+]

8.4 = -log [H3O+]

[H3O+] = 3.981*10^-9 M

Answer: 4*10^-9 M

C)

use:

[OH-] = Kw/[H3O+]

Kw is dissociation constant of water whose value is 1.0*10^-14 at 25 oC

[OH-] = (1.0*10^-14)/[H3O+]

[OH-] = (1.0*10^-14)/(6*10^-10)

[OH-] = 1.667*10^-5 M

Answer: 2*10^-5 M

D)

use:

[OH-] = Kw/[H3O+]

Kw is dissociation constant of water whose value is 1.0*10^-14 at 25 oC

[OH-] = (1.0*10^-14)/[H3O+]

[OH-] = (1.0*10^-14)/(4*10^-9)

[OH-] = 2.5*10^-6 M

Answer: 3*10^-6 M