1. Introduction to Acids and Bases

2. Introduction Cont.
Acids and bases are a way of classifying compounds based upon what happens to them when you place them in water.
An acid is a substance that releases hydrogen ions when dissolved in water.
A base is a substance that releases hydroxide ions when dissolved in water.

4. ACIDS

5. Two types of Acids-
Organic –derived from plant & animals
Mineral- derived from minerals

6. Characteristics of Acids
Sour taste(for edible acids).
Turn blue litmus paper red
All mineral and few organic acid soluble in water

7. May burn your skin. Sulphuric acid most corrosive
May burn your skin. Sulphuric acid most corrosive. Carbonic acid weakest acid.
Concentrated mineral acids and formic acid & acetic acid have a strong pungent smell.

8. Other Examples of Acids
HCl Hydrochloric Acid
H2SO4 Sulfuric Acid
CH3COOH Acetic Acid (Vinegar)

9. Common Acids
Vinegar (acetic or ethanoic acid)
Citric Acid

10. Arrehenius concept of acids

11. Arrhenius Definition of Acids and Bases
Acids produce hydrogen ions (H+) in an aqueous solution, while bases produce hydroxide ion (OH-).
Acid: HCl (aq) H+ (aq) + Cl- (aq)
Base: NaOH(aq) Na+(aq) + OH-(aq)

12. DEGREE OF DISSOCIATION
Property of a substance that tells us how many molecules of the substance will actually produce free ions in water.
Example of acetic acid
CH3 COOH → CH3 COO - + H+
No of hydrogen atoms present in acetic acid- 4
No of hydrogen ions are free- 1

13. Strong acids – completely dissociate in their solution
Strong acids – completely dissociate in their solution. Ex-nitric acid, sulphuric acid Weak acids-partially dissociate in their solution

14. Acids A dilute acid has lots of water and a small amount of acid
A concentrated acid has lots of acid and not much water so must be handled carefully
A strong acid releases lots of H+
A weak acid releases fewer H+

15. BASES

16. Common Bases
Ammonia

17. Characteristics of Bases
Bitter taste (for edible bases only)pungent smell. Most of them are colourless solids Exceptions are the hydroxides of iron and copper
Solutions of bases are soapy to touch &Feels slippery
Turn litmus from red to blue.

18. Most bases are insoluble in water
Most bases are insoluble in water. Exception NaOH, KOH, barium hydroxide, calcium hydroxide
Bases that are soluble in water are called alkalies.Ex- sodium hydroxide.
Alkalies have corrosive action on skin.

19. Other examples of Bases
Sodium Hydroxide NaOH
Potassium Hydroxide KOH
Ammonia NH3

20. pH The term pH is a measure of the acidity or basicity of a solution.
pH stands for potential of hydrogen.The hydrogen content of a solution determines whether it is acidic or basic

21. The extent to which a compound is acidic or basic is measured by the- pH indicator. A pH indicator is a substance that changes colour around a particular pH value

22. Measuring acid strength?
To decide if something is an acid or a base we can use an indicator.
Litmus and Universal Indicator are examples of indicators.
They change colour depending on if they are in an acid or a base.

23. Identifying Acids and Bases
Acids have a ph from 0-7
Lower pH value indicates a stronger acid.
Bases have a pH from 7-14
Higher pH value indicates a stronger base.

24. Did we Miss something??
What happens when the pH of a substance is 7?

25. Why Learn about Acids & Bases?
What do you think is the pH level of tap water?
Is it important for Lakes & Rivers to maintain a certain pH?

26. Situations in which pH is controlled
“Heartburn”
Planting vegetables and flowers
Fish Tanks and Ponds
Blood
Swimming pools

27. Acid Rain
Pollution in the air (sulfur dioxide, carbon dioxide, nitrogen dioxide) combines with water to form various acids. .

29. pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335