Name ____________________________________________ Date _________________________ Period__
Sample Problems for Chapter 14: Acids and Bases
14.6 The pH Scale
(Read pgs. 458-464 in the chemistry textbook)
1. Locate and label each of the following on the pH scale below:
a) neutral pH
b) use an arrow to show the 'range' of increasingly acidic pH values
c) use an arrow to show the 'range' of increasingly basic pH values
d) draw a box around the pH that is 100X more basic than pH 10
e) draw a triangle around the the pH that is 1,000X more acidic than pH 9
f) underline the pH of hydrochloric acid
g) draw a circle around the pH of 1.0M NaOH (lye)
The pH Scale
1
2
3
4
5
6
7
8
9
10
11
12
13
14
2. Fill in the following table to the relationship of pH values to [H+]
Solution
Acidic
[H+]
pH
Neural
Basic
3. Identify the regions of the pH scale where:
a) [H+] is increasing relative to neutral
b) H+] is decreasing relative to neutral
c) [OH-] is increasing relative to neutral
d) [OH-]is decreasing relative to neutral
The pH Scale
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2
3
4
5
6
7
8
9
10
11
12
13
14
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4. Consider the pH of the following items:
Item
root beer
kitchen cleaner
pickles
glass cleaner
cranberry juice
pH
5.8
10.9
3.5
7.6
2.9
a) Place the pH values of the items on the list in order of most acidic to most basic.
Most
Most
Acidic
Basic
b) Which item has the highest [H+]?
____________________
c) Which item has the highest [OH-]?
____________________
5. If the pH of a solution reads 4.00, is the solution
acidic / basic / neutral ?
(circle one)
6. What does it mean when we say that the pH scale is a logarithmic scale?
2
[H+] is the antilog of the pH
6. Continued:
7.
a) what is the [H+] of a solution with a pH of 2.00?
Is this solution acidic or basic?
_______________________ = __________
b) what is the [H+] of a solution with a pH of 2.50?
Is this solution acidic or basic?
____________________
________________________= __________
d) what is the [H+] of a solution with a pH of 12.0?
Is this solution acidic or basic?
____________________
________________________= __________
c) what is the [H+] of a solution with a pH of 8.30?
Is this solution acidic or basic?
____________________
____________________
________________________
= __________
3
e) what is the [H+] of a solution with a pH of 6.20?
____________________
Is this solution acidic or basic?
_______________________ =__________
+
8. Conversely, if you already know the [H ] value, you can find out the pH by taking the log of the [H+].
This answer will be ( − ), so we multiply the answer by −1 to make the answer ( + )
pH is the negative log (base 10) of the [H+] concentration
a) what is the pH of a solution with an [H+] of 1 x 10-6 M?
Is this solution acidic or basic?
_______________________
b) what is the pH of a solution with an [H+] of 1 x 10-10 M?
Is this solution acidic or basic?
_______________________
_______________________
c) what is the pH of a solution with an [H+] of 1.5 x 10-1 M?
Is this solution acidic or basic?
_______________________
______________________
_______________________
d) what is the pH of a solution with an [H+] of 3.66 x 10-5 M? ______________________
Is this solution acidic or basic?
_______________________
4
e) what is the pH of a solution with an [H+] of 5 x 10-8 M? _______________________
Is this solution acidic or basic?
_______________________
9. If you know the [H+] it is easy to find the [OH-] concentration by remembering that KW = [H+] [OH-] and
that the value of KW = 1.0 x 10-14 M
(a) What is the [OH-] of a solution with an [H+] of 3.7 x 10-3?
(b) What is the [OH-] of a solution with an [H+] of 5.5 x 10-13?
(c) What is the [OH-] of a solution with an [H+] of 2.5 x 10-9?
10. Conversely, if you already know the [H+] you can use the KW to calculate the [OH-] value.
(a) What is the [H+] of a solution with an [OH-] of 2 x 10-10?
5
(b) What is the [H+] of a solution with an [OH-] of 3.8 x 10-4?
12. What is the pOH
scale?
13. The antilog of the [OH-] will give the pOH value.
pOH is the negative log (base 10) of the OH-] concentration
a) what is the pOH of a solution with an [OH-] of 1 x 10-6 M?
_____________________
b) what is the pOH of a solution with an [OH-] of 1 x 10-10 M?
_____________________
c) what is the pOH of a solution with an [OH-] of 1.5 x 10-1 M?
____________________
14. The sum of the pH and the pOH will always equal 14 - so if you know either value you can quickly
calculate the other value by subtracting:
(a) What is the pH of a solution with a pOH of 10.0?
(a) What is the pOH of a solution with a pH of 5.0?
_______________________
_______________________
6
(a) What is the pH of a solution with a pOH of 7.5?
_______________________
15. Why does a neutral solution have a pH of 7.00?
16. If you know the [OH-], how can you determine the pH of solution?
STEP 1:
STEP 2:
17. Calculate the pH of each solution given the following [H+] or [OH-] values:
(a) [OH-] = 1.0 x 10-5 M
STEP 1: _______________________
STEP 2: _______________________
(b) [OH-] = 2.5 x 10-11
STEP 1: _______________________
STEP 2: _______________________
(c) [H+] = 1.0 x 10-4
STEP 1: _______________________
(d) [OH-] = 8.2 x 10-4
STEP 1: _______________________
STEP 2: _______________________
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(e) [H+] = 3.6 x 10-9
STEP 1: _______________________
18. A solution with a pH of 3 is 10 times more acidic than a solution with a pH of 4. Explain.
19. State whether each of the following solutions is acidic, basic, or neutral:
__________
(a) soda, pH 3.22
__________
(b) laundry detergent, pOH 4.56 → 14.00 - 4.56 = 9.44 pH
__________
(c) honey, pH 3.9
__________
(d) shampoo, pOH 8.3 → 14.00 - 8.3 = 5.70 pH
__________
(e) rain, pH 5.8
__________
(f) cheese, pH 7.4
__________
(g) coffee, pH 5.52
__________
(h) drain cleaner, pOH 2.8 → 14.00 - 2.8 = 11.20 pH
__________
(i) tomatoes, pH 4.2
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