1. Seminar: Chemistry of Acids and Bases
Freddie Arocho-Perez
Kaplan University
SC155: Introduction to Chemistry

2. Acids
An acid is a substance that produces hydrogen ions, H+, when dissolved in water.
Example: HCl (Hydrochloric acid) in water.

3. Acids
The strength of an acid is based on the concentration of H+ ions in the solution.
The more H+ ions, the stronger is the acid.

4. Acids
Examples:
Sulfuric acid, H2SO4, is manufactured in greater quantity than any other industrial chemical. It is the acid found in automobile batteries.
Hydrochloric acid, HCl, is “stomach acid” in the digestive systems of most mammals.
Phosphoric acid, H3PO4, is used to manufacture phosphate fertilizers. The tart taste of many soft drinks is due to the presence of phosphoric acid.

5. Bases
A base is a substance that produces hydroxide ions, OH-, when dissolved in water.
Example: NaOH (Sodium hydroxide) in water.

6. Bases
The strength of a base is determined by the concentration of hydroxide ions (OH-).
The greater the concentration of OH- ions, the stronger is the base.
Mixtures containing bases are often called alkaline.

7. Bases
Examples:
Sodium hydroxide, NaOH, or lye, is used in the production of aluminum, glass, and soap. Drain cleaners often contain NaOH because it reacts with the fats and proteins found in grease and hair.
Calcium hydroxide, Ca(OH)2 , or slaked lime, is made industrially by treating lime (CaO) with water. It is used in mortars and cements.
Magnesium hydroxide, Mg(OH)2, or milk of magnesia, is an additive in foods, toothpaste, and many over-the-counter medications. Many antacids contain magnesium hydroxide.

8. Neutralization Reaction
When solutions (mixtures) of an acid and a base are combined, the products are a salt and water.
Acids and bases react to neutralize each other:
HCl + NaOH --> NaCl + H2O
Example:
HBr + KOH --> KBr + H2O

9. Neutralization Reaction
Observe the reaction between Milk of Magnesia, Mg(OH)2, and HCl.
Milk of magnesia is a mixture of magnesium hydroxide, Mg(OH)2, in water.
The magnesium hydroxide dissolves upon the addition of the acid.

10. Neutralization Reaction

11. pH Scale
The strength of an acid or base in a solution is measured on a scale called the “pH scale”.
pH, or “potential of Hydrogen”, is the scale that measures the relative acidity or alkalinity (basic) of a solution.
Solutions are measured from 0 (totally acid) to 14 (totally alkaline or basic), and 7 is neutral.
Acidic solution: pH < 7
Neutral solution: pH = 7
Basic solution: pH > 7

12. pH Scale

13. pH Scale
An acid-base indicator is a dye that changes color depending on the pH of the solution.

14. pH Scale
For more accurate measurements, a pH meter can be used, which measures the voltage in the solution.

15. pH in Biological Systems
All living things are water-based systems, which mean that they depend heavily on aqueous equilibria, especially acid-base equilibria.
Acid-base and pH concepts are extremely important to Biochemistry, which is the study of the chemistry of biological systems.

16. pH in Biological Systems
Reasons why we should be concerned about pH in biological systems:
It gives a qualitative measure for many problems in cell biology and related fields.
The cell environment is always buffered at approximately pH = 7 (water).
Enzymes are sensitive to pH. The optimal pH for most enzymes fall in the range of 6 to 8.
Pepsin, a digestive enzyme in the stomach, works best at pH = 2.

17. pH and Blood
The optimum blood pH in a healthy body is slightly alkaline and falls within the narrow range of 7.35 and 7.45.
The human body is made of about 75% water, which is necessary for the transportation of nutrients, oxygen, and other biochemical substances.
It is important for this water-based medium to be pH balanced.

18. pH and Blood
The normal pH of blood running through arteries (large elastic-walled blood vessels that carry blood from the heart to other parts of the body) is 7.45.
The pH of blood in the veins (vessels that transports blood to the heart) is about 7.35.
A variety of factors affect blood pH including what is ingested, vomiting, diarrhea, lung function, endocrine function, kidney function, and urinary tract infection.

19. pH in Urine, Saliva, Stomach
Normal urine pH averages about 6.0.
Saliva has a pH between 6.0 and 7.4.
Normal stomach pH is between 1.0 and 2.0.

20. Acids and the Stomach A peptic ulcer, or lesion in the stomach wall.
Ulcers occur when the protective mucosal lining is penetrated and gastric acid begins to dissolve the stomach.

21. Acids and the Stomach
Common over-the-counter antacid remedies are bases:
Gaviscon: Al(OH)3
Maalox: Al(OH)3 and Mg(OH)2
Mylanta: Al(OH)3 and Mg(OH)2
Milk of magnesia: Mg(OH)2

22. Acids and the Stomach
Dissolution testing is a test for measuring the performance of a drug product.
Tablets or capsules taken orally remain one of the most effective means of treatment available.
The effectiveness of such dosage forms relies on the drug dissolving in the fluids of the gastrointestinal tract prior to absorption.

23. Acid Rain
Sulfur oxide, SO3, is a by-product of the burning of coal or oil.
It reacts with moisture in the air to form sulfuric acid, H2SO4.
It is primarily responsible for acid rain.
Statue adorning the Rheims Cathedral in France has been severely eroded by acid rain.

24. Acid Rain
pH Values from freshwater sites across the United States, 2007.

25. Acid Rain
High acidity in rainfall causes corrosion in building materials.
Marble and limestone (calcium carbonate) react with the acid; structures made from them erode.
This statue at the Field Museum in Chicago shows the effects of corrosion from acid rain and atmospheric pollutants (a).
The same statue after restoration (b).

26. A solution of which pH is acidic?
Practice Exercises
A solution of which pH is acidic? 2 7 8 10

27. Practice Exercises
A solution of which pH is acidic? 2 7 8 10

28. The pH of a solution is 9.3. This solution is _____.
Practice Exercises
The pH of a solution is 9.3. This solution is _____.
Acidic
Basic
Neutral
None of the above

29. Basic Practice Exercises
The pH of a solution is 9.3. This solution is _____.
Acidic
Basic
Neutral
None of the above

30. In a neutralization reaction, the products are _______.
Practice Exercises
In a neutralization reaction, the products are _______.
Salts
A salt and water
A salt and acid
An acid and a base

31. A salt and water Practice Exercises
In a neutralization reaction, the products are _______.
Salts
A salt and water
A salt and acid
An acid and a base