CHAPTER 14 AP CHEMISTRY

NATURE OF ACIDS AND BASES Acids - sour Acids - sour Bases (alkali) - bitter and slippery Bases (alkali) - bitter and slippery Brønsted-Lowry Brønsted-Lowry Acid is a proton [H + ] donor, base is a proton acceptor Acid is a proton [H + ] donor, base is a proton acceptor H + never found in water, will always form the hydronium ion H + never found in water, will always form the hydronium ion HA(aq) + H 2 O(l) --> H 3 O + (aq) + A - (aq) HA(aq) + H 2 O(l) --> H 3 O + (aq) + A - (aq) Acid Base Conj. Acid Conj. Base Acid Base Conj. Acid Conj. Base k a = [H + ][A - ] k a = [H + ][A - ] [HA] [HA] Diprotic acid - forms two protons Diprotic acid - forms two protons Page 627 table 14.1 Page 627 table 14.1

Continue Carboxyl group Carboxyl group Page 628 table 14.2 Page 628 table 14.2 Arrange the following species to strength as a base H 2 O, F -, CN -, Cl -, NO 2 - Arrange the following species to strength as a base H 2 O, F -, CN -, Cl -, NO 2 -

WATER AS AN ACID OR BASE Amphoteric - can be either an acid or base OH- — H2O — H3O+ NH2- — NH3 — NH4+ Any aqueous solution that contains H3O+ ions and OH- ions will eventually reach equilibrium 2 H2O <==> H3O+(aq) + OH-(aq)

Continue Any pure solids or liquids do not have concentrations, therefore they are not placed in the equation Any pure solids or liquids do not have concentrations, therefore they are not placed in the equation k w = [ H 3 O + ][OH - ] = 1.0 X at 25 °C k w = [ H 3 O + ][OH - ] = 1.0 X at 25 °C When [ H 3 O + ] = [OH - ] = 1.0 X a reaction will be neutral When [ H 3 O + ] = [OH - ] = 1.0 X a reaction will be neutral [ H 3 O + ] < [OH - ] the solution is basic [ H 3 O + ] < [OH - ] the solution is basic [ H 3 O + ] > [OH - ] the solution is acidic [ H 3 O + ] > [OH - ] the solution is acidic Calculate the [H 3 O + ] or [OH - ] opposite of what you have and state if the solution is neutral, acidic, or basic Calculate the [H 3 O + ] or [OH - ] opposite of what you have and state if the solution is neutral, acidic, or basic 2.0 X M H 3 O X M H 3 O X M OH X M OH X M OH X M OH - Orange juice demo Orange juice demo

pH SCALE pH = -log [H + ] pH = -log [H + ] Significant figures of the concentration is equal to the number of places after the decimal point. Significant figures of the concentration is equal to the number of places after the decimal point. 1.0 X two sig. figs. so the pH will have two decimal places pH = X two sig. figs. so the pH will have two decimal places pH = 9.00 pOH = -log[OH - ] pOH = -log[OH - ] pk = -log k pk = -log k [H+] = 10 -pH [H+] = 10 -pH pH = 7 neutral, pH 7 basic pH = 7 neutral, pH 7 basic

STRONG ACIDS HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 4, HClO 3 HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 4, HClO 3 Look for the major components found in the solution Look for the major components found in the solution HCl(aq) has H +, Cl -, and H 2 O HCl(aq) has H +, Cl -, and H 2 O Look at what can give H + Look at what can give H + H 2 O H + + OH - H 2 O H + + OH - HCl ---> H + + Cl - HCl ---> H + + Cl - Water gives such a small amount of hydrogen ions we can ignore it Water gives such a small amount of hydrogen ions we can ignore it

WEAK ACID HF(aq) species are H +, F -, H 2 O. Look at those which can give H + HF(aq) species are H +, F -, H 2 O. Look at those which can give H + HF(aq) H + (aq) + F - (aq) k a = 7.2 X HF(aq) H + (aq) + F - (aq) k a = 7.2 X H 2 O(aq) H + (aq) + OH - (aq) k a = 1 X H 2 O(aq) H + (aq) + OH - (aq) k a = 1 X HF is a weak acid but it is stronger than water so it is the dominant source of H + HF is a weak acid but it is stronger than water so it is the dominant source of H + HX(aq) + H 2 O(l) H 3 O+(aq) + X - (aq) HX(aq) + H 2 O(l) H 3 O+(aq) + X - (aq)

Continue Go over example page 639 Go over example page 639 % dissociation = amount dissociated X 100 % dissociation = amount dissociated X 100 Initial concentration Initial concentration Page 641 example Page 641 example STRONG BASES - group 1 metals, calcium, barium, and strontium STRONG BASES - group 1 metals, calcium, barium, and strontium

AMINE GROUPS B(aq) + H 2 O(l) BH + (aq) + OH - (aq) B(aq) + H 2 O(l) BH + (aq) + OH - (aq) k b = [BH + ][OH - ] k b = [BH + ][OH - ] [B] [B] Page 647 table 14.3 Page 647 table 14.3 Page example Page example k a X k b = k w k a X k b = k w

POLYPROPTIC ACID Can furnish more than one proton Can furnish more than one proton H 3 PO 4 H + + H 2 PO 4 - k a = 7.5 X H 3 PO 4 H + + H 2 PO 4 - k a = 7.5 X H 2 PO 4 - H + + HPO 4 2- k a = 6.2 X H 2 PO 4 - H + + HPO 4 2- k a = 6.2 X HPO 4 2- H + + PO 4 3- k a = 4.8 X HPO 4 2- H + + PO 4 3- k a = 4.8 X With each proton lost the ka becomes smaller With each proton lost the ka becomes smaller Page 651 table 14.4 Page 651 table 14.4 Page 651 example Page 651 example metallic oxides are strong bases metallic oxides are strong bases O 2- + H 2 O 2OH - O 2- + H 2 O 2OH -

ACID-BASE PROPERTIES OF SALT SOLUTIONS Cations Cations Spectators - derived from a strong base Spectators - derived from a strong base Li +, Na +, K +, Ca 2+, Sr 2+, Ba 2+ Li +, Na +, K +, Ca 2+, Sr 2+, Ba 2+ Acidic - all other cations (transition metals included) Acidic - all other cations (transition metals included) Anions Anions Spectators - derived from a strong acid Spectators - derived from a strong acid Cl -, Br -, I -, NO 3 -, ClO 4 -, SO 4 2- Cl -, Br -, I -, NO 3 -, ClO 4 -, SO 4 2- Basic - derived from a weak acid Basic - derived from a weak acid F -, NO 2 -, CO 3 2- F -, NO 2 -, CO 3 2- If the cation is acidic and anion basic, you look at their k a and k b If the cation is acidic and anion basic, you look at their k a and k b

ACID-BASE CHARACTERS Any molecule with a H-X bond can be an acid IF TWO rules are followed Any molecule with a H-X bond can be an acid IF TWO rules are followed In general metal hydrides are basic or have no acid-base properties In general metal hydrides are basic or have no acid-base properties Nonmetal hydrides are acidic or have no acid- base properties Nonmetal hydrides are acidic or have no acid- base properties Pages examples and tables 14.5, 14.6, 14.7 Pages examples and tables 14.5, 14.6, 14.7 Read Read