2. ACIDS, BASES & SALTS

3. The Arrhenius Theory of Acids and Bases

4. Arrhenius Theory of Acids and Bases: an acid contains hydrogen and ionizes in solutions to produce H + ions: HCl  H + (aq) + Cl - (aq)

5. Arrhenius Theory of Acids and Bases: a base contains an OH - group and ionizes in solutions to produce OH - ions: NaOH  Na + (aq) + OH - (aq)

6. Neutralization Neutralization: the combination of H + with OH - to form water. H + (aq) + OH - (aq)  H 2 O (l) Hydrogen ions (H + ) in solution form hydronium ions (H 3 O + )

7. In Reality… H + + H 2 O  H 3 O + Hydronium Ion (Can be used interchangeably with H + )

8. Commentary on Arrhenius Theory… One problem with the Arrhenius theory is that it’s not comprehensive enough. Some compounds act like acids and bases that don’t fit the standard definition.

9. Bronsted-Lowry Theory of Acids & Bases

10. Bronsted-Lowry Theory of Acids & Bases: An acid is a proton (H + ) donor A base is a proton (H + ) acceptor

11. for example… HCl (aq) + H 2 O (l)  H 3 O + (aq) + Cl - (aq) Proton transfer Acid Base

12. NH 3 (aq) + H 2 O (l)  NH 4 + (aq) + OH - (aq) BASE ACID CONJUGATE ACID CONJUGATE BASE Ammonia is a proton acceptor, and thus a base another example… Water is a proton donor, and thus an acid.

14. Conjugate acid-base pairs Conjugate acid-base pairs differ by one proton (H + ) A conjugate acid is the particle formed when a base gains a proton. A conjugate base is the particle that remains when an acid gives off a proton.

15. Examples: In the following reactions, label the conjugate acid-base pairs: H 3 PO 4 + NO 2 -  HNO 2 + H 2 PO 4 - CN - + HCO 3 -  HCN + CO 3 2- HCN + SO 3 2-  HSO 3 - + CN - H 2 O + HF  F - + H 3 O + acidbasec. acidc. base acidbasec. acidc. base acid base c. acid c. base acidbase c. acidc. base

16. Amphoteric Substances A substance that can act as both an acid and a base (depending on what it is reacting with) is termed amphoteric. Water is a prime example.

17. Properties of Acids and Bases ACIDS Have a sour taste Change the color of many indicators Are corrosive (react with metals) Neutralize bases Conduct an electric current BASES Have a bitter taste Change the color of many indicators Have a slippery feeling Neutralize acids Conduct an electric current

18. Other Household Acids and Bases Antacid: a weak base that neutralizes excess stomach acid. The pH of shampoo is generally kept between 5 and 8. Lemon juice is an acid that is sometimes used to help keep fruit looking fresh. What will happen to left apple?

19. Indicators- “Way Cool” Cyber-lab: http://www.miamisci.org/ph/phlemon.ht ml

20. Strength of Acids and Bases A strong acid dissociates completely in sol’n: HCl  H + (aq) + Cl - (aq) A weak acid dissociates only partly in sol’n: HNO 2  H + (aq) + NO 2 - (aq) A strong base dissociates completely in sol’n: NaOH  Na + (aq) + OH - (aq) A weak base dissociates only partly in sol’n: NH 3 (aq) + H 2 O (l)  NH 4 + (aq) + OH - (aq)

21. The Lewis Theory of Acids and Bases

22. The Lewis Theory of Acids & Bases Lewis acid: a substance that can accept an electron pair to form a covalent bond (electron pair acceptor). Lewis base: a substance that can donate an electron pair to form a covalent bond (electron pair donor).

23. Neutralization Neutralization: the formation of a coordinate covalent bond in which both electrons originated on the same (donor) atom.

24. Example 1: Ionization of NH 3 : NH 3 + H 2 O  NH 4 + + OH - N N H H H OHH+  H H H HH + O.. + - acid base

25. Example 2: Auto-ionization of water: H 2 O + H 2 O  H 3 O + + OH - O O HH OHH+  H HHH + O.. + - acid base..

26. Example 3: Reaction of NH 3 with HBr (a Lewis AND a Bronsted-Lowry acid-base reaction): NH 3 + HBr  NH 4 + + Br - N N H H H BrH+  H H H H +.. + - acid base

27. Acid Base Theories Lewis Bronsted-Lowry Arrhenius

28. SUMMARY OF ACID-BASE THEORIES TheoryAcid DefinitionBase Definition Arrhenius Theory Any substance which releases H + ions in water solution. Any substance which releases OH - ions in water solution Brǿnsted- Lowry Theory Any substance which donates a proton. Any substance which accepts a proton. Lewis Theory Any substance which can accept an electron pair. Any substance which can donate an electron pair.

29. Acid-Base Reactions Neutralization reactions: reactions between acids and metal hydroxide bases which produce a salt and water. H + ions and OH - ions combine to form water molecules: H + (aq) + OH - (aq)  H 2 O (l)

30. Example 1: the reaction of HCl and NaOH (there are 3 ways to write the chemical equation): Balanced formula unit equation: HCl (aq) + NaOH (aq)  H 2 O (l) + NaCl (aq) Total ionic equation: H + (aq) +Cl - (aq) +Na + (aq) +OH - (aq)  H 2 O (l) +Na + (aq) +Cl - (aq) Net ionic equation: H + (aq) + OH - (aq)  H 2 O (l)

31. Example 2: Write the 3 types of equations for the reaction of hydrobromic acid, HBr, with potassium hydroxide, KOH. Balanced formula unit equation: HBr (aq) + KOH (aq)  H 2 O (l) + KBr (aq) Total ionic equation: H + (aq) +Br - (aq) +K + (aq) +OH - (aq)  H 2 O (l) +K + (aq) +Br - (aq) Net ionic equation: H + (aq) + OH - (aq)  H 2 O (l)

32. Example 3: Write the 3 types of equations for the reaction of nitric acid, HNO 3, with calcium hydroxide, Ca(OH) 2. Balanced formula unit equation: 2HNO 3 (aq) + Ca(OH) 2 (aq)  2H 2 O (l) + Ca(NO 3 ) 2 (aq) Total ionic equation: 2H + (aq) +2NO 3 - (aq) +Ca 2+ (aq) +2OH - (aq)  2H 2 O (l) +Ca 2+ +2NO 3 - (aq) Net ionic equation: H + (aq) + OH - (aq)  H 2 O (l)