Chemistry Reference
In-Depth Information
Example 2
What is the pH of a solution with a pOH value of 3?
Answer: pH = 14 - pOH = 14 - 3 = 11
Now, let's try an example that requires you to use the “log” button on
your calculator. Try this with your calculator and see if you can get the
same answer as shown.
Example 3
What is the pH of a solution with a [H
3
O
+
] of 7.4 × 10
-4
?
Answer: pH = -log[H
3
O
+
] = -log(7.4 × 10
-4
) = 3.13076828,
which we round to 3.1
What if you're given the concentration of the hydroxide (OH
-
) ion in-
stead of the hydronium (H
3
O
+
) ion? You make use of both of the formulas
that we used in Example 2 and Example 3.
Example 4
What is the pH of a solution with a [OH
-
] concentration of 8.2 × 10
-8
?
Answer: pH = 14 - pOH = 14 - (-log[OH
-
]) = 14 - (-log(8.2 × 10
-8
))
= 6.9, after rounding
Lesson 9-2 Review
For questions 1-6, determine if each statement is describing an acid or
a base.
1.
It reacts with some metals to produced hydrogen gas.
2.
It turns litmus paper red.
3.
It has pH values greater than 7.
4.
It often tastes sour or tart.
5.
Sodium hydroxide (NaOH) is an example.
6.
It turns litmus paper blue.
7.
What would be the pOH value of a solution with a [OH
-
] of 1 × 10
-5
?
