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pH
Name . . . . . . . . . . . . . . .
Hydrogen Ion Concentration
in MOLES/LITER at 25° C
pH
H+
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
(10 )1
(10-1)0.1
(10-2)0.01
(10-3)0.001
(10-4)0.0001
(10-5)0.00001
(10-6)0.000001
(10-7)0.0000001
(10-8)0.00000001
(10-9)0.000000001
(10-10)0.000000001
(10-11)0.0000000001
(10-12)0.00000000001
(10-13)0.000000000001
(10-14)0.0000000000001
0
OH+
0.0000000000001(10-14)
0.000000000001(10-13)
0.00000000001(10-12)
0.0000000001(10-11)
0.000000001(10-10)
0.00000001(10-9)
0.0000001(10-8)
0.000001(10-7)
0.00001(10-6)
0.0001(10-5)
0.0001(10-4)
0.001(10-3)
0.01(10-2)
0.1(10-1)
1(100)
pH = -log[H+]
1) What is a mole?
The more hydrogen ions in a solution the more acidic it becomes.
HYDROGEN ION CONCENTRATION
Moles per liter
MONTH
1
.000000026
Sci Not:
2
.00000031
Sci Not:
3
.000000042
Sci Not:
4
.00000000061
5
.000000066
6
.000074
Sci Not:
Sci Not:
Sci Not:
2) Convert the hydrogen ion concentration to scientific notation. What do you notice?
Notice the magnitude of change from month 4 to 6. This change is equivalent to the magnitude difference
between 105 and 1010 or the difference between 100,000 and 10,000,000,000.
Create a line graph of the data. (month, hydrogen ion concentration)
USE A GRAPHING CALCULATOR (TI-83)
1. STAT – Edit - Enter data
3. STAT PLOT (set up line graph with large markers)
4. GRAPH
3) Comment on your graph
2. Set WINDOW or ZOOM – Zoomstat
Is it an accurate display of your data?
Sketch the shape
Anything you notice?
(You might try throwing out month 6 to get a better look at months 1-5)
Now take the log of the concentrations.
What do all these values have in common?
Instead of working with all negative values it would be easier to work with the opposite of these numbers.
The opposite of the common logarithm of the hydrogen ion concentration is known as pH
pH stands for the "power of hydrogen."
The pH scale ranges from 0 to 14.
Neutral water has a pH of 7.
4) What is a mathematical synonym for power?
5) A logarithm is an
?
pH or "power of hydrogen" is a logarithm or in other words an exponent.
6) Which month was the concentration of hydrogen ions the greatest?
7) How does the pH of this month compare with the pH of the other months?
Make a line graph of the pH of the stream using your calculator.
8) Comment on your graph
Is it an accurate display of your data?
Sketch the shape
Anything you notice?
More acidic compounds have a greater hydrogen ion concentration.
9) Large hydrogen ion concentrations correspond with what kind of pH value (smaller, larger)?
Example: Hydrochloric acid has 2.5 x 10 -2 moles per liter.
10) What is the pH?
More alkaline compounds have a smaller hydrogen ion concentration.
11) Small hydrogen ion concentrations correspond with what kind of pH value (smaller, larger)?
Example: Lye soap suds have 9 x 10-12 moles per liter.
12) What is the pH?
Let f(x) be the function that converts hydrogen ion concentration to pH.
f(x) = -log x
Where: x = hydrogen ion concentration in moles per liter AND f(x) = pH
13) Find the inverse function f-1(x).
This inverse function will convert pH to hydrogen ion concentration.
14) Use this function to find the hydrogen ion concentration when the pH is:
4.2 (pH of tomatoes):
2.8 (pH of ordinary vinegar):
7.2 (pH of human blood):
Work:
15) A change in pH from 8.1 to 9.9 represents how many times as many hydrogen ions?
Work: