1. October 27, 20151 Acids and Bases Chapter 16 Pages 614 - 652

2. October 27, 20152 Arrhenius Definition of Acids & Bases Acids release H + ions when dissolved in water. – HCl(g)  H + (aq) + Cl - (aq) Bases release OH - ions when dissolved in water. – NaOH(s)  Na + (aq) + OH - (aq)

3. October 27, 20153 HCl(g)  H + (aq) + Cl - (aq)

4. October 27, 20154 NaOH(s)  Na + (aq) + OH - (aq)

5. October 27, 20155 Limitations of Arrhenius Concept: Restricted to aqueous solutions More general definition offered independently by Johannes Bronsted and Thomas Lowry (1923) Focuses on the transfer of H + ions from one substance to another An H + ion is simply a proton with no surrounding valence electrons; interacts strongly with nonbonding electons pairs of water molecules to form hydronium ions, H 3 O + (aq)

6. October 27, 20156

7. 7 Reaction between HCl and NH 3 (all gases)

8. October 27, 20158 HCl acts as a Bronsted-Lowry Acid; Water is the base.

9. October 27, 20159 Ammonia is a B-L base; Water is the acid.

10. October 27, 201510

11. October 27, 201511 Bronsted-Lowry Acids & Bases An acid is a substance that can donate a proton to another substance. A base is a substance that can accept a proton. A tug-of-war between an acid & base for proton (in the form of H + ) Because the emphasis is on proton transfer, can be applied to non-aqueous reactions, too.

12. October 27, 201512 A substance can function as an ACID only if another substance simultaneously behaves as a BASE. Acid – must have a H atom to lose as an H + ion Base – must have a nonbonding pair of electrons to bind to H + ion.

13. October 27, 201513 Stupid Sports Analogy… Acids are the quarterback, throwing away a PROTON (football) Bases are the receivers, catching the PROTON, (football)

14. October 27, 201514 Conjugate Acid-Base Pairs Consider a reversible reaction: HX (aq) + H 2 O  X - (aq) + H 3 O + (aq)

15. October 27, 201515 When reaction is reversed, X - acts as base and H 3 O + acts as acid. HX (aq) + H 2 O(l)  X - (aq) + H 3 O + (aq) Every acid has a conjugate base, formed by removing a proton from the acid. HX (aq) acid X - (aq) conjugate base H 2 O (l) base H 3 O + (aq) conjugate acid

16. October 27, 201516 Conjugate Acid-Base Pairs

17. October 27, 201517 Another Example

18. October 27, 201518 And another,

19. Conjugate Acid-Base Pairs HBr(aq) + H 2 O (l)  If HBr is the acid and H 2 O is the base, write the rest of the reaction…..  Br - (aq) + H 3 O + (aq) Br - (aq) is the conj. Base H 3 O + (aq) is the conj. Acid October 27, 201519