2. Section 18-1 Section 18.1 Introduction to Acids and Bases Identify the physical and chemical properties of acids and bases. Lewis structure: a model that uses electron-dot structures to show how electrons are arranged in molecules Classify solutions as acidic, basic, or neutral. Compare the Arrhenius, Brønsted-Lowry, and Lewis models of acids and bases.

3. 2 Properties of Acids þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) þ Taste sour þ Corrode metals þ Good Electrolytes þ React with bases to form a salt and water þ pH is less than 7 þ Turns blue litmus paper to red “Blue to Red A-CID” Acids

4. Some Common Acids HC 2 H 3 O 2 acetic acidin vinegar HCl hydrochloric acidstomach acid H 3 C 6 H 5 O 7 citric acidfruits H 2 CO 2 carbonic acidsoft drinks H 3 PO 4 phosphoric acidsoft drinks

5. Acid Nomenclature Flowchart

6. Name Them! HI (aq) HBr H 2 SO 3 HNO 3 HIO 3

7. 6 Properties of Bases  Generally produce OH - ions in water  Taste bitter, chalky  Are electrolytes  Feel soapy, slippery  React with acids to form salts and water  pH greater than 7  Turns red litmus paper to blue “Basic Blue” Bases

8. Some Common Bases NaOHsodium hydroxide lye KOHpotassium hydroxide liquid soap Ba(OH) 2 barium hydroxide stabilizer for plastics Mg(OH) 2 magnesium hydroxide Milk of magnesia Al(OH) 3 aluminum hydroxide Maalox (antacid)

9. Section 18-1 Properties of Acids and Bases (cont.) All water solutions contain hydrogen ions (H + ) and hydroxide ions (OH – ). acidic solution contains more hydrogen ions than hydroxide ions. basic solution contains more hydroxide ions than hydrogen ions.

10. Section 18-1 Properties of Acids and Bases (cont.) The usual solvent for acids and bases is water—water produces equal numbers of hydrogen and hydroxide ions in a process called self-ionization. H 2 O(l) + H 2 O(l) ↔ H 3 O + (aq) + OH – (aq) The hydronium ion is H 3 O +.

11. Section 18-1 The Arrhenius Model The Arrhenius modelArrhenius model identifies acids as substances that ionize in water to produce hydronium ion – HCl ionizes to produce H + ions. – HCl(g) → H + (aq) + Cl – (aq) identifies bases as substances that ionize in water to produce hydroxide ion – NaOH dissociates to produce OH – ions. – NaOH(s) → Na + (aq) + OH – (aq)

12. Not everyone was happy with Arrhenius’s definition A major problem with the Arrhenius definition of acids and bases is that it limits acids and bases to water (aqueous) solutions. Since an acid requires water to ionize and form hydronium ions, there can be no Arrhenius acids unless water is involved as the solvent.

13. Arrhenius Acids/Bases only exist in water solutions. Bronsted- Lowry Acids/Bases can exist when no water is present All Arrhenius acids and bases can also be classified as Bronsted-Lowry acids and bases.

14. Bronsted and Lowry felt that this was too limiting, since there are many non-aqueous systems (no water is present). They came up with the following definitions for acids and bases. an acid is a hydrogen ion donor a base is a hydrogen ion acceptor The Brønsted-Lowry Model is a more inclusive model of acids and bases. The Brønsted-Lowry Model

15. Section 18-1 The Brønsted-Lowry Model (cont.) conjugate acid is produced when a base accepts a hydrogen ion. conjugate base is produced when an acid donates a hydrogen ion. conjugate acid-base pair consists of two substances related to each other by donating and accepting a single hydrogen ion.

16. Teacher-student model Teachers give off information (like acids give off protons) Students accept information (like bases accept protons) Sometimes teachers are students, and sometimes students are teachers Teacher and students are roles that individuals play depending on the situation. Acid and base are roles that molecules play in a particular chemical reaction. In different reactions they may play different roles.

17. Section 18-1 The Brønsted-Lowry Model (cont.) Hydrogen fluoride—a Brønsted-Lowry acid –HF(aq) + H 2 O(l) ↔ H 3 O + (aq) + F – (aq) (acid) (base) (C.A.) (C.B.)

18. Section 18-1 The Brønsted-Lowry Model (cont.) Ammonia— Brønsted-Lowry base –NH 3 (aq) + H 2 O(l) ↔ NH 4 + (aq) + OH – (aq) (base) (acid) (conjugate acid) (conjugate base) Water and other substances that can act as acids or bases are called amphoteric.amphoteric

19. Section 18-1

20. The Lewis Model According to the Lewis model, a Lewis acid is an electron-pair acceptor and a Lewis base is an electron pair donor.Lewis model The Lewis model includes all the substances classified as Brønsted-Lowry acids and bases and many more.

21. A.A B.B C.C D.D Section 18-1 Section 18.1 Assessment A Lewis acid is a(n) ____. A.electron pair donor B.hydrogen ion donor C.electron pair acceptor D.substance that contains an hydroxide group

22. A.A B.B C.C D.D Section 18-1 Section 18.1 Assessment A conjugate acid is formed when: A.a base accepts a hydrogen ion B.an acid accepts a hydrogen ion C.an acid donates a hydrogen ion D.a base donates a hydrogen ion

23. Section 18-2 Section 18.2 Strengths of Acids and Bases Relate the strength of an acid or base to its degree of ionization. Compare the strength of a weak acid with the strength of its conjugate base. Explain the relationship between the strengths of acids and bases and the values of their ionization constants. In solution, strong acids and bases ionize completely, but weak acids and bases ionize only partially.

24. Strong/Weak Acids Acids can be either strong electrolytes or weak electrolytes. Strong acids (such as HCl) completely break up into their ions: HCl (aq)  H + (aq) + Cl - (aq) Weak acids (such as HC 2 H 3 O 2 ) only partially break up into their ions: HC 2 H 3 O 2  H + (aq) + C 2 H 3 O 2 - (aq) Weak acids don’t completely break up because they go to equilibrium! Strengths of Acids

25. Section 18-2 Strengths of Acids The equilibrium constant, K eq, provides a quantitative measure of the degree of ionization of an acid. acid ionization constant, K aacid ionization constant K a is a measure of how much H3O+ is produced The higher the K a, the stronger the acid K a indicates whether products or reactants are favored at equilibrium.

26. Strong/Weak Bases Bases can be either strong electrolytes or weak electrolytes. Strong bases (such as NaOH) completely break up into their ions: NaOH (aq)  Na + (aq) + OH - (aq) Weak bases (such as NH 3 ) only partially break up into their ions: NH 3 (aq) + H 2 O  NH 4 + (aq) + OH - (aq) Weak bases don’t completely break up because they go to equilibrium! Strengths of Bases

27. Section 18-2 Strengths of Bases base ionization constant, K bbase ionization constant K b is a measure of how much OH- is produced the higher the K b, the stronger the base

28. A.A B.B C.C D.D Section 18-2 Section 18.2 Assessment A solution with a small K b is a ____. A.weak acid B.weak base C.strong acid D.strong base

29. A.A B.B C.C D.D Section 18-2 Section 18.2 Assessment Where is the equilibrium point in the ionization equation for a strong acid? A.far right B.far left C.slightly right D.slightly left