NAME:_______________________________________________
➢ The pH of a solution indicates how acidic or basic that solution is:
pH range:
0-6.99
7
7.01-14
Solution type:
Acidic
Neutral
Basic
➢ The pH and pOH are reflections of the [H3O+1] and the [OH-1] of a solution, and since we
know that the [H3O+1] x [OH-1] = 10-14 M2, we can use this to define an important fact:
pH + pOH = 14
Let’s start simple…
[H3O+1]
pH
[OH-1]
pOH
Solution?
10-5 M
5
10-9 M
9
Acidic
10-11 M
7
10-12 M
4
➢ Easy, right? Well, how would you find the pH of a solution that has a [H 3O+1] of
2.74 x 10-4 M? Well, the answer is 3.56. How did Mr. Senn do that???
The “POWER of the LOG!”
pH = -log [H3O+1]
and
pOH = -log [OH-1]
Now, do these calculations:
1.
What is the pH of a solution if the [H3O+1] = 3.54 x 10-2 M? ______________
2.
What is the pOH of a solution if the [OH-1] = 7.12 x 10-11 M? _____________
3.
What is the pH of a solution if the pOH = 12.4? ______________
➢ NOW, tell what type of solution the following situations describe (acidic, basic or neutral):
*Remember, you always need to find the pH to do that!!!
1.
[H3O+1] = 2.56 x 10-9 M
2.
pOH = 12
3.
[OH-1] = 2.95 x 10-6 M
➢ So, what if you want to find the [H3O+1] from a pH? Well, when the pH is simple like 5, the
concentration is 10-5 M! What about if the pH is 8.44? The [H3O+1] is 3.63 x 10-9 M. Again,
how did Mr. Senn do that??? Well, we can reverse the log and come up with this:
[H3O+1] = 10-pH
and
[OH-1] = 10-pOH
Now, do these calculations:
1.
What is the [H3O+1] of a solution that has a pH of 2.2?
2.
What is the [H3O+1] of a solution that has a pOH of 4.4? careful!