1. Acids and Bases

2. Acids and Bases
We encounter acids and bases everyday

3. Acids and Bases Acids (taste sour) Bases (taste bitter, feel slippery)
flavorings (citrus, vinegar)
household products (plastic, detergent, batteries)
acid rain
Bases (taste bitter, feel slippery)
soaps
antacid (tums, rolaids)

4. Acid Reactions Acids react with metals to produce hydrogen gas
Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)

5. Acid Reactions
Acids react with metal carbonates and hydrogen carbonates to produce carbon dioxide
NaHCO3(s) + HC2H3O2(aq)  NaC2H3O2(aq) + H2O(l) + CO2(g)
geologists can identify a rock as limestone by putting a few drops of hydrochloric acid on it and watching for bubbles of carbon dioxide to form

6. Identifying Acids or Bases
litmus is a dye that can distinguish solutions of acids and bases
aqueous solutions of acids turn blue litmus paper pink
aqueous base solutions turn red litmus paper blue

7. Identifying Acids or Bases
Acids and bases also conduct electricity
That makes them electrolytes

8. What makes a solution acidic or basic?
Why are some things acidic and some things are basic?
The relative concentrations of:
hydrogen ions [H+]
hydroxide ions [OH-]

9. [H+] and [OH-] If [H+] is greater than [OH-], its an acid
If [H+] is less than [OH-], its a base
If [H+] =[OH-], its neither-its neutral

10. [H+] and [OH-] The solvent for acids and bases is usually water
When water ionizes it forms equal amounts of H+ and OH-
H2O  H OH-
Since [H+] = [OH-], water is neutral

11. Arrhenius Acid and Bases
Arrhenius was a Swedish chemist (1883) that wondered how aqueous solutions became acidic or basic.
An acid is a substance containing hydrogen that ionizes in water to produce H+ ions in solution
HCl(g) + H2O  H3O+(aq) + Cl- (aq)

12. Vocabulary Word
Arrhenius acid: a substance containing hydrogen that ionizes in water to produce H+ ions in solution

13. Arrhenius Acid and Bases
base: substance containing a hydroxide group (OH-) that dissociates to produce OH- ions in solution
NaOH(s) H2O  Na+(aq) + OH-(aq)

14. Vocabulary Word
Arrhenius base: substance containing a hydroxide group (OH-) that dissociates to produce OH- ions in solution

15. Problem
Not all bases contain OH- groups

16. Revised Model
In 1923 Bronsted (a Danish scientist) and Lowry (a British scientist) independently proposed a model that focuses on H+ ions
Bronsted-Lowry model
acids are H+ donors
bases are H+ acceptors.

17. Vocabulary Word Bronsted-Lowry acid: H+ donor
Bronsted-Lowry base: H+ acceptor

18. Bronsted-Lowry Acids and Bases
HX + H2O  H3O X-
acid base conjugate conjugate
acid base
The reaction in both directions involves an acid and a base
The base becomes the conjugate acid after it receives the proton
The acid becomes the conjugate base after it donates the proton

19. Vocabulary Words
conjugate acid: the species produced when a base accepts a hydrogen ion from an acid
conjugate base: the species produced when an acid donates a hydrogen ion to a base

20. Acid Base Reactions acid base conj. acid conj. base
Every Bronsted-Lowry interaction involves conjugate acid-base pairs
Identify the acid, base, conjugate acid and conjugate base:
acid
base
conj. acid
conj. base

21. Bronsted-Lowry Bases
Ammonia is a base according to the Bronsted-Lowry model, because it can accept a hydrogen ion

22. Identify the Species conj. base conj. acid acid base conj. acid
water can be an acid or a base so it’s amphoteric