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Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
187
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 18
pOH ϭ 14.00 Ϫ 3.14 ϭ 10.86
The pOH of the solution is 10.86.
As you might expect, the carbonated soft drink is acidic.
Practice Problems
7. Calculate the pH and pOH of aqueous solutions having the following ion concentrations.
a. [H ϩ ] ϭ 1.0 ϫ 10 Ϫ14 M
b. [OH Ϫ ] ϭ 5.6 ϫ 10 Ϫ8 M
c. [H ϩ ] ϭ 2.7 ϫ 10 Ϫ3 M
d. [OH Ϫ ] ϭ 0.061M
Calculating ion concentrations from pH When the pH of a
solution is known, you can determine the concentrations of H ϩ and
OH Ϫ . First, recall the equation for pH.
pH ϭ Ϫlog [H ϩ ]
Multiply both sides of the equation by Ϫ1.
ϪpH ϭ log [H ϩ ]
Now take the antilog of both sides of the equation.
antilog (ϪpH) ϭ [H ϩ ]
Rearrange the equation.
[H ϩ ] ϭ antilog (ϪpH)
A similar relationship exists between [OH Ϫ ] and pOH.
[OH Ϫ ] ϭ antilog (ϪpOH)
Example Problem 18-4
Calculating [H ϩ ] and [OH Ϫ ] from pH
What are [H ϩ ] and [OH Ϫ ] in an antacid solution with a pH of 9.70?
Use pH to find [H ϩ ].
[H ϩ ] ϭ antilog (ϪpH)
[H ϩ ] ϭ antilog (Ϫ9.70)
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