CHM 1025C Module Eight-Chapter 15.8-15.9 Name:__Answers___
Part L: pH Scale Calculations (Section 15.8-15.9) 10 points
What is the pH and pOH of the following solutions:
pOH = 14.00 –
pH Kw
= 1.00 x 10-14 = [H3O1+][OH1-] [H3O1+]
is the same as [H1+]
(1) 0.0100 M HCl
pH = -Log [H+] = -Log
[0.0100] = 2.00
pOH = 14.00 –
pH =
14.00 – 2.00 = 12.00
(2) 0.0055 M Mg(OH)2
The dissociation
reaction: Mg(OH)2 ↔
Mg 2+ + 2 OH 1-
A 0.0055 M Mg(OH)2 solution produces a 2 x 0.0055 M hydroxide ion or
0.0110 M hydroxide ion
pOH = -Log [OH-] = -Log [0.0110] = 1.96
pOH = 14.00 –
pH =
14.00 – 1.96 = 12.04
(3) The pH of vinegar is 2.85,
calculate the [H3O1+]:
[H+] = 10–pH = 10-2.85 = 0.00141
M
(4) Easy Off Oven Cleaner has a pH of 11.70. What is the [H3O1+]
and [OH 1- ]?
[H+] = 10–pH = 10-11.70 =
1.995 x 10-12 M
pOH = 14.00 –
pH =
14.00 – 11.70 = 2.30
[OH-] = 10–pOH = 10-2.30 = 0.00501 M