1. The Chemistry of Acids and Bases
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2. Learning Objectives
12.1C: Acids and bases Learners be able to calculate, recognize, and understand 1) acidity/alkalinity in aqueous solution that Arrhenius and Bronsted-Lowry are equivalent 2) proton donors and bases are proton acceptors 3) pH as -log10[H+], and be able to convert pH to concentration and the reverse pH for a strong acid be able to calculate the pH of a strong acid and a strong base 4) know that water is weakly dissociated 5) know the ionic product of water, Kw and that Kw = [H+] [OH-]

3. New Terms Hydronium Ion which is (H3O+) pH = Log 10 or power of H+
Amphiprotic like frogs
or writing with both hands
4) Conjugate = Latin word
conjugare, like conjoined

4. Acids

5. Bases

6. Some Operational Properties of Acids
Produce H+
Taste sour. Ex: Vinegar is acetic acid and citrus fruits contain citric acid
Corrode metals and produce hydrogen gas
Electrolytes
React with carbonates and bicarbonates to produce CO2(g)
React with bases to form a salt and water
pH is less than 7
Turns blue litmus paper to red “Blue to Red A-CID”

7. How can we identify strong acids or bases? Easy, memorize them!
Strong Acids and Bases
How can we identify strong acids or bases? Easy, memorize them!
Memorized Strong Acids
HClO4
H2SO4 HI
HBr
HCl
HNO3

9. Acid Nomenclature Review
No Oxygen
w/Oxygen
An easy way to remember which goes with which…
“In the cafeteria, you ATE something ICky”

10. Acid Nomenclature Review
HBr (aq)
H2CO3
H2SO3
 hydrobromic acid
 carbonic acid
 sulfurous acid

11. Some Properties of Bases
Produce OH- ions in water
Taste bitter, chalky
Are electrolytes
Feel soapy, slippery
React with acids to form salts and water
pH greater than 7
Turns red litmus paper to blue “Basic Blue”

12. ALL Strong Bases become
Some Common Bases
NaOH sodium hydroxide lye
KOH potassium hydroxide liquid soap
Ba(OH)2 barium hydroxide stabilizer for plastics
Mg(OH)2 magnesium hydroxide MOM” Milk of magnesia
Al(OH)3 aluminum hydroxide Maalox (antacid)
ALL Strong Bases become
OH-

13. Acid/Base definitions
Definition #1: Arrhenius (traditional)
Acids – produce H+ ions
Bases – produce OH- ions
(Problem: some bases don’t have hydroxide ions!)

14. Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water

15. Arrhenius: acids and bases
Acid: Substance that, when dissolved in water, increases the concentration of hydrogen ions (protons, H+).
Base: Substance that, when dissolved in water, increases the concentration of hydroxide ions or OH-

16. How can we identify strong acids or bases?
Strong Acids and Bases
How can we identify strong acids or bases?
HCl
HNO3 HI
HBr
HClO4
H2SO4
YOU DO THE REST

17. Definitions #2 Definition #2: Brønsted – Lowry Acids – proton donor
Bases – proton acceptor
A “proton” is really just a hydrogen atom that has lost it’s electron!

18. B/L Acid is a substance that produces H+ (H3O+) in water
A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor
Lowry
Bronsted
B/L base is a substance that produces OH- in water.
A Brønsted-Lowry base is a proton acceptor
base
conjugate acid
conjugate base
acid

19. When there is NO charge
The Brønsted definition means NH3 is a BASE in water — and water is itself an ACID…must have a removable (acidic) proton. HCl, H2O, H2SO4
A Brønsted–Lowry BASE…must have a pair of nonbonding electrons, or a negative charge.NH3, H2O, SO3-2

20. If it can be either…
...it is amphiprotic.
HCO3–
HSO4 –
H2O

22. Water, Water Everywhere
Autoionization
Kw = [H3O+] [OH-] = x at 25 oC
In a neutral solution [H3O+] = [OH-]
so Kw = [H3O+]2 = [OH-]2
and so [H3O+] = [OH-] = 1.00 x 10-7 M

23. pH of Common Substances

24. pH
pH is defined as the negative base-10 logarithm of the hydronium ion concentration.
pH = –log [H3O+]

25. (Remember that the [ ] mean Molarity, or mol/L)
Calculating the pH
pH = - log [H+]
(Remember that the [ ] mean Molarity, or mol/L)
Example: If [H+] = 1 X pH = - log 1 X 10-10
pH = - (- 10)
pH = 10
Example: If [H+] = 1.0 X 10-5 pH = - log 1.0 X 10-5
pH = - (- 5)
pH = 5

26. A pH Number line
Number lines have been used in history and math classes, so to keep up we use them in chemistry classes.
[H+] =10-15
[OH -] = 101
[H+] < [OH -]
basic
pH = 15
[H+] =10-12
[OH -] = 10-2
basic
pH = 12
[H+] < [OH -]
basic
[H+] = 10-7
[OH -] = 10-7
[H+] = [OH -]
neutral
pH = 7
acidic
[H+] = 10-2
[OH -] = 10-12
[H+] > [OH -]
acidic
pH = 2

27. Try These! Find the pH of these:
A 0.15 M solution of Hydrochloric acid
Answer: pH (- 2 sig figs)
2) A 3.00 X 10-7 M solution of Nitric acid
Answer: pH (- 3 sig figs) remember leading zero do NOT count

28. pH calculations – Solving for H+
If the pH of Coke is 3.12, [H+] = ???
Because pH = - log [H+] then
- pH = log [H+]
Take antilog (10x) of both sides and get
10-pH = [H+]
[H+] = = 7.6 x 10-4 M
*** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button

29. pH calculations – Solving for H+
A solution has a pH of What is the Molarity of hydrogen ions in the solution?
pH = - log [H+]
8.5 = - log [H+]
-8.5 = log [H+]
Antilog -8.5 = antilog (log [H+])
= [H+]
3.16 X 10-9 = [H+]

30. The “other” “p” Scale
The “p” in pH tells us to take the negative log of the quantity (in this case, hydronium ions).
Some similar examples are
pOH –log [OH-]

31. pOH Acids and bases are opposites, pH and pOH are opposites!
pOH does not really exist, but it is useful for changing bases to pH. No one uses the scale
pOH looks at the perspective of a base
pOH = - log [OH-]
Since pH and pOH are on opposite ends,
pH + pOH = 14

32. [H3O+], [OH-] and pH What is the pH of the 0.0010 M NaOH solution?
[OH-] = (or 1.0 X 10-3 M)
pOH = - log
pOH = 3
pH = 14 – 3 = 11
OR Kw = [H3O+] [OH-]
[H3O+] = 1.0 x M
pH = - log (1.0 x 10-11) = 11.00

33. If you know one, you know them all:
[OH-]
1.0 x 10-14
[OH-]
10-pOH
1.0 x 10-14
[H+]
-Log[OH-]
[H+]
pOH
10-pH
14 - pOH
-Log[H+]
14 - pH pH

34. Calculating [H3O+], pH, [OH-], and pOH
Problem 1:
A chemist dilutes concentrated hydrochloric acid to make a solution of M.
Calculate the [H3O+], pH, [OH-], and pOH
ANSWERS: pH=2.62, pOH = 11.38, 4.2x10 -12
Problem 2:
What is the [H3O+], [OH-], and pOH of a solution with pH = 3.67? Is this an acid, base, or neutral?
ANSWERS : An acid. [H3O+], M, [OH-], 4.7x10-11
pOH = 10.33

36. ANSWERS to Previous Slide