1. Today’s assignment: Textbook P567; 11-17, 21; 569 34, 35
Warning—anyone putting your head down or sleeping in this class will receive a one hour detention.
What is hijklmno?
Answer: H20
What is the name of James bond’s Eskimo cousin?
Answer: polar bond

2. EC what blood pH is dangerous?
What does titration mean?

3. Yesterday’s assignment
Read Page In Review Book
Do page185: 46, 47, 50, 51, 53, 54

4. Let’s take a look at titration one more time.

5. You are about to find out—I hope!!
Acid, base, or neutral?
The pH scale.
What the heck is pH anyway? And why are the numbers so weird? Why is acid 1-6 and base is 8-14?
You are about to find out—I hope!!

6. pH is impossible to understand unless you know two facts you don’t know now:
Ok hold on to your hats. When you have pure H2O, there are already H+ and OH- ions present!!!
This is because water dissociates naturally to form both H+ ions and OH- ions.
HOH H+ + OH-
When it does, it forms both ions at a concentration of 1 x so they are equal in concentration. The solution is neither acid nor base.
This relationship is mathematical—as the concentration of one goes up the other must go down. The product is always equal to 1 x
This can be seen in an animation of water collisions.
Note that collisions cause the dissociation.

7. Fact 2: we have two things going on but we only talk about one
Fact 2: we have two things going on but we only talk about one! Let me show you.

8. Notice that as one goes up the other goes down
Notice also that with each step, the change is by a factor of ten.
So we wind up with a situation like this:

9. In a neutral solution, the concentrations of each ion are equal.
Of course when base is added, the opposite happens
When acid is added, the base is reduced and the acid is increased.

11. So I still don’t know what pH is!!
To understand pH, just remember some basic math:
A power of 10 can be expressed as a single number called the log. So the log of
107 is 7 and the log of 106 is 6.

12. So how does pH work? PH stands for “potential for hydrogen”.
Since pH involves hydrogen, we ignore hydroxide. So even though we know one goes up while the other goes down, we only talk about H!
So a pH of 2 means H is high and hydroxide is low.
Next, we get rid of the negative exponents, by defining pH as the negative log of the concentration.
A pH of 7 means they are equal
So it looks like this: all you see is positive numbers!!
A pH of 12 means H is low and hydroxide is high
That’s why the numbers are so weird!!!

13. Here’s the most important facts about pH:
pH numbers of 0- 6 are acid
2. A pH number of 1 is stronger than 6.
A pH number of 2 is ten times stronger than a 3.
4. A pH of seven is neutral
5. Ph numbers of 8-14 are base.
6. A ph of 11 is ten times stronger than a pH of 10.

14. Acid Base neutral 1 7 14 Possible chart: Base increasing
Acid decreasing
1x x x 100
neutral

15. Also you can determine the source of the ph number is the exponent left when you get rid of the rest
Must add to -14
There are implication to this. If the water is in soil then of course the soil could be acidic or basic. See quiz—slaked lime question.

16. Let’s try some problems!

19. End

20. How do we know what an unknown substance is?
We use substances that indicate whether a substance is acid or base, and sometimes indicate the pH.
So they are called “indicators”.
Go to page 5 of the reference table to see the indicators you will be responsible for.

21. Look at bromthymol blue
How do they work?
Look at bromthymol blue
There are two numbers
6.0 – 7.6
yellow to blue
And two colors
yellow
blue
Here’s how they work: the first number tells you that all pH numbers lower than 6 and up to 6 the solution is yellow so pH of 5 is yellow
Any pH 7.6 or above the color of the solution is blue.
In between there may be other colors but overall you change from yellow to blue.

22. So the pH range is between 4.4 and 5
A solution tests as orange in methyl orange, but red on litmus paper. What is the pH range of the solution?
Answer: the orange test tells you the solution must be greater than But the litmus tells you it is less than 5.
So the pH range is between 4.4 and 5

23. Let’s see some actually work.

24. Acids and bases have two different faces
How are they used on exams? Try this:
A solution gives a yellow color with Bromthymol blue and a yellow color with methyl orange. What is the pH range of the solution.
Answer:
Acids and bases have two different faces

25. Demo Question: What is the pH of the solution as tested?

28. June 09’

29. June 06’