Substances, Mixtures, and Solubility - McGraw-Hill Higher Education
Substances, Mixtures, and Solubility - McGraw-Hill Higher Education
Substances, Mixtures, and Solubility - McGraw-Hill Higher Education
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pH Levels Most life-forms<br />
can’t exist at extremely<br />
low pH levels. However,<br />
some bacteria thrive in<br />
acidic environments.<br />
Acidophils are bacteria<br />
that exist at low pH levels.<br />
These bacteria have been<br />
found in the Hot Springs of<br />
Yellowstone National Park<br />
in areas with pH levels<br />
ranging from 1 to 3.<br />
What is pH<br />
You’ve probably heard of pH-balanced shampoo or deodorant,<br />
<strong>and</strong> you might have seen someone test the pH of the water<br />
in a swimming pool. pH is a measure of how acidic or basic a<br />
solution is. The pH scale ranges from 0 to 14. Acidic solutions<br />
have pH values below 7. A solution with a pH of 0 is very acidic.<br />
Hydrochloric acid can have a pH of 0. A solution with a pH of 7<br />
is neutral, meaning it is neither acidic nor basic. Pure water is<br />
neutral. Basic solutions have pH values above 7. A solution with<br />
a pH of 14 is very basic. Sodium hydroxide can have a pH of 14.<br />
Figure 18 shows where various common substances fall on the<br />
pH scale.<br />
The pH of a solution is related directly to its concentrations<br />
of hydronium ions (H 3<br />
O ) <strong>and</strong> hydroxide ions (OH ). Acidic<br />
solutions have more hydronium ions than hydroxide ions.<br />
Neutral solutions have equal numbers of the two ions. Basic<br />
solutions have more hydroxide ions than hydronium ions.<br />
In a neutral solution, how do the numbers of<br />
hydronium ions <strong>and</strong> hydroxide ions compare<br />
Figure 18 The pH scale classifies<br />
a solution as acidic, basic,<br />
or neutral.<br />
pH Scale The pH scale is not a simple linear scale like mass or<br />
volume. For example, if one book has a mass of 2 kg <strong>and</strong> a second<br />
book has a mass of 1 kg, the mass of the first book is twice<br />
that of the second. However, a change of 1 pH unit represents a<br />
tenfold change in the acidity of the solution. For example, if one<br />
solution has a pH of 1 <strong>and</strong> a second solution has a pH of 2, the<br />
first solution is not twice as acidic as the second—it is ten times<br />
more acidic. To determine the difference in pH strength, use the<br />
following calculation: 10 n , where n the difference between<br />
pHs. For example: pH3 pH1 2, 10 2 100 times more acidic.<br />
Vinegar<br />
Egg white<br />
Hydrochloric<br />
acid<br />
Gastric contents Milk Baking<br />
soda<br />
Ammonia<br />
Sodium hydroxide<br />
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14<br />
Soft drinks<br />
Blood plasma<br />
Milk of<br />
magnesia<br />
Tomatoes<br />
236 CHAPTER 8 <strong>Substances</strong>, <strong>Mixtures</strong>, <strong>and</strong> <strong>Solubility</strong><br />
(tl tr)Elaine Shay, (tcl)Brent Turner/BLT Productions, (tcr)Matt Meadows, (bl bcl)CORBIS, (bcr)Icon Images, (br)StudiOhio
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