1. Unit 9: Acid/Base Chemistry
Chemistry CPA 2014

2. Demo – Rainbow in a Cylinder
What do you think?
What causes a color change?
What is an acid? Give examples.
What is a base? Give examples.
Do they mix together or react with one another?

3. Examples of every acids and bases
Lemons
Orange Juice
Vinegar
Car batteries
Stomach Acid
Soft drinks
Vitamin C
Asprin
Bases:
Mustards
Antacids (TUMS)
Drain-o
Soap
Detergents
Fertilizers
Lawn lime
Baking soda
Coffee

4. More Everyday Acids and Bases

5. Acids Acids - react with certain metals have a sour taste
are caustic, i.e. they "eat through" many materials
turn indicators certain distinctive colors. e.g., turn litmus red.
Conduct electricity

6. Bases Bases react with certain other metals have a bitter taste
are also caustic
turn indicators other distinctive colors. e.g., turn litmus blue.
Conduct electricity

7. Measuring Acid & Base levels
Indicators
Turn a certain color according to the amount of hydrogen ions (H+) or hydroxide ions (OH-) pH
A scale used to quantify the strength of an acid or base.

8. Defining Acids – Atomic Style!
An acid is a substance that produces hydronium ions in water.
A hydronium ion consists of a hydrogen ion attached to a water molecule:
Hydronium = H3O+

9. Defining Bases – Atomic Style!
A base is a substance that produces hydroxide ions (OH-) when it dissolves in water.

10. pH
A quantitative measure to express the concentration of hydronium ions [H+] in a solution.
pH means “power of hydrogen”

11. The pH Scale – in pictures!

12. pH Scale Low pH (0-7) High pH (7-14) pH of 7 high amount of H+
Low amount of OH-
acid
High pH (7-14)
small amount of H+
High amount of OH-
base
pH of 7
Equal amounts of H+ and OH-
neutral

13. pH Scale in more color…

14. Formulas – pH pH = -log [H+]
Note: Molarity is commonly abbreviated by using square brackets, thus [H+] = hydrogen ion concentration

15. Problem #1 Calculate the pH if the [H+] = 1 x 10-4 M pH = -log [H+]
pH = -log [1x10-4]
pH = 4
acidic

16. Formulas - pOH
Power of hydroxide ion
pOH = - log [OH-]

17. Problem #2 Calculate the pOH if the [OH-] = 1x10-2 pOH = - log[1x10-2]

18. Relationship between pH and pOH
pH + pOH = 14
So if the pOH is 2,
then the pH is 12 and basic
Always use pH to determine if the solution is acidic or basic

19. Practice Assignment [H+] pH [OH-] pOH Acidic or Basic 1 1 x 10-5 59
Acidic 2 7 3
1 x 10-4 4
1 x 10-2 11

20. Strength vs. Concentration
The strength of an acid is related to the proportion of which it has reacted with water to produce ions.
Strong acid/base means it separates into ions in solution very easily.
Weak acid/base means it doesn’t separate into ions in solution as much.
The concentration tells you about how much of the original acid/base is dissolved in the solution.

21. Strong vs. Weak
Notice how strength means separation (how much they split), not concentration (how many there are)

22. Buffers
A buffer resists change to pH when a small amount of acid or base is added to a solution.
Can be used in a pool or a lake
Your body has natural buffers to maintain the pH of certain organs

23. Strong Example: HCl  H+ + Cl-
Buffers are made of…
A weak acid and its salt
H2PO4- ↔ H HPO4-2
A weak base and its salt
NH3 + HOH ↔ NH OH-
Remember strength is determined by its ability to dissociate (into ions) in solution
Strong Example: HCl  H Cl-

24. Neutralization Reaction
A reaction between an acid and a base
The products are always a salt and water
Acid + Base  a Salt + Water
A salt is the substance formed when the cation of the base combines with the anion of the acid. These substances generally have a neutral pH.

25. Example HCl + NaOH  NaCl + HOH
acid base  sodium chloride (a salt) + water
2HCl + Mg(OH)2 
MgCl HOH
stomach acid + base  neutral products
Demo: Upset Tummy? MOM to the Rescue!

26. Neutralization Reaction Practice Problems
For each of the following reactants, predict the products:
H2CO3 and Sr(OH)2 __________ + H2O
HClO4 and NaOH  _________ + _________
HBr and Ba(OH)2 _________ + __________

27. Predict the Acid and the Base from the Salt.
For each of the following salts, tell which acid and based formed it.
Predict the Acid and the Base from the Salt.
Salt
Acid
Base
Zn(NO3)2
Al(ClO)3
NaCl
Ca3(PO4)2
(NH4)2C2O­4

28. Acid Rain environmental problem
affects large parts of the US and Canada
damaging to lakes, streams, and forests and the plants and animals that live in these ecosystems.

29. Effects of Acid Rain Damage to plants Damage to animals
Damage to buildings

33. Effects of Acid Rain on Marble (marble is calcium carbonate)
George Washington:
BEFORE acid rain
George Washington:
AFTER acid rain

34. Acid rain affects the whole world – no part of the world is safe.
Where is Acid Rain?
Acid rain affects the whole world – no part of the world is safe.

36. Causes of Acid Rain Natural Sources: Man-Made Sources: volcanoes
decaying vegetation
Forest fires
lightning
Man-Made Sources:
emissions of sulfur dioxide (SO2)
Emissions of nitrogen oxides (NOx)

38. In the United States, roughly 2/3 of all SO2 and 1/4 of all NOx come from electric power generation that relies on burning fossil fuels, like coal. 
Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds.
The result is a mild solution of sulfuric acid and nitric acid.

41. wet deposited material dry deposited material
2 Types of Acid Rain
wet deposited material
dry deposited material

42. Wet Deposition acidic rain, fog, and snow
If the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain, snow, fog, or mist.
The strength of the effects depends on several factors:
how acidic the water is
the chemistry of the soils involved
the types of fish, trees, and other living things that rely on the water.

43. Dry Deposition
In areas where the weather is dry, the acid chemicals may become incorporated into dust or smoke and fall to the ground sticking to the ground, buildings, homes, cars, and trees.
Dry deposited gases and particles can be washed from these surfaces by rainstorms, leading to increased runoff.
This runoff water makes the resulting mixture more acidic.
About half of the acidity in the atmosphere falls back to earth through dry deposition.

44. Measuring Acid Rain
Normal rain is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid, giving the resulting mixture a pH of approximately 5.6 at typical atmospheric concentrations of CO2.
As of 2000, the most acidic rain falling in the U.S. has a pH of about 4.3.

45. Reducing Acid Rain Societal changes Individual action
Use Alternative Energy Sources
Restore a Damaged environment
Individual action
Turn off lights, computers, and other appliances when you're not using them.
Use energy-efficient appliances
Keep your thermostat at 68°F in the winter and 72°F in the summer.
Insulate your home as best you can.
Carpool, use public transportation, or better yet, walk or bicycle whenever possible
Buy vehicles with low NOx emissions, and properly maintain your vehicle.

46. Clean Air Act Amendments – 1990
imposes emission restrictions on fossil fueled power plants