Introduction to Acids and Bases Chapter 19 Sections 1, 2, plus some of 3 and 4 Honors Chemistry Dr. Knorr Adapted from http://www.chemistryconnections.com/acids%20bases/acids%20bases%20intro.ppt

Some Common Acids HCl hydrochloric acid HNO3 nitric acid H3PO4 phosphoric acid H2SO4 sulfuric acid HC2H3O2 acetic acid (vinegar) lemon juice

Acids Electrolytes Taste sour Corrode metals React with many bases to form salts and water

Some Common Bases NaOH sodium hydroxide KOH potassium hydroxide Mg(OH)2 magnesium hydroxide Al(OH)3 aluminum hydroxide NH3 ammonia

Bases Taste bitter, chalky Are electrolytes Feel soapy, slippery React with many acids to form salts and water

Arrhenius Acids and Bases Acids produce H+ in aqueous solutions water HCl H+(aq) + Cl- (aq) Bases produce OH- in aqueous solutions NaOH Na+(aq) + OH- (aq)

Brønsted-Lowry Acids and Bases Acids donate H+ in aqueous solutions water HCl H+(aq) + Cl- (aq) Bases accept H+ in aqueous solutions NH3 + H2O NH4+(aq) + OH- (aq) All Arrhenius A/B are B-L A/B

Lewis Acids and Bases Acids accept electron pairs in aqueous solutions Bases donate electron pairs in aqueous solutions H F H F H N + B F H N B F

Conjugate Acids and Bases A conjugate acid-base pair is related by loss/gain of one hydrogen ion. NH3 + H2O NH4+(aq) + OH- (aq) Base acid conjugate acid conjugate base gain H+ lose H+

pH Indicates the acidity [H+] of the solution pH = - log [H+] [H+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11 M 11

pOH Indicates the basicity (aka alkalinity) [OH-] of the solution pOH = - log [OH-] [OH-] pOH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11 M 11

pH Range [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] Acidic Basic

Why 0  14? Autoionization of water H2O H+ + OH- In pure water, [H+] = [OH-] = 1 x 10-7 M so [H+] x [OH-] = 1 x 10-14 Another important relationship: pH + pOH = 14

pH, pOH, [H+], and [OH-] [H+] pH pOH [OH-] 1 x 10-5 M 5 9 1 x 10-9 M 2.4 3.98 x 10-3 M 11.6 2.51 x 10-12 M

Acids H+ OH- Increase H+ HCl (g) H+ (aq) + Cl- (aq) More [H+] than water alone As H+ increases, OH- decreases [H+] > [OH-] water H+ OH-

pH of Some Common Acids gastric juice 1.0 lemon juice 2.3 vinegar 2.8 orange juice 3.5 coffee 5.0 milk 6.6

Acids Strong Acids (the big 7): HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3 Example: HCl(aq) H+ (aq) + Cl- (aq) **Strong acids completely ionize

Acids Weak acids: HC2H3O2, HF, (and all others) Example: HF(aq) H+ (aq) + F-(aq) ** Weak acids ionize only slightly

Bases Increase the hydroxide ions (OH-) NaOH (s) Na+(aq) + OH- (aq) More [OH-] than water, [OH-] When OH- increases, H+ decreases [OH] > [H+] OH- H+

pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4 milk of magnesia 10.6 household ammonia 11.0

Bases Strong Bases (the big 8) Example: Group I metal hydroxides Heavier group II metal hydroxides Ca(OH)2, Ba(OH)2, Sr(OH)2 Example: NaOH(aq)  Na+ (aq) + OH- (aq) **Strong bases completely ionize

Bases Weak Bases Example: NH3(aq) +H2O NH4+ (aq) + OH-(aq) NH 3 (ammonia) Example: NH3(aq) +H2O NH4+ (aq) + OH-(aq) ** Weak bases ionize only slightly

Neutralization Reactions When STRONG acids and STRONG bases are mixed in the right amounts, the resulting solution is neutral. NaOH (aq) + HCl(aq) NaCl(aq) + H2O(l) base acid salt water Ca(OH)2 (aq) + 2 HCl(aq) CaCl2(aq) + 2H2O(l) base acid salt water **An acid/base reaction is a special form of a double replacement reaction

Neutralization The cation from the base and the anion from the acid combine to form a salt. Simultaneously, H+ and OH- combine to produce water. NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) H+ + OH-  H2O (or HOH) from acid from base water Na+ + Cl-  NaCl from base from acid salt

Learning Check AB1 Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit

Solution AB1 Describe each solution as: 1) acid 2) base or 3) neutral. A. _1_ soda B. _2_ soap C. _1_ coffee D. _1_ wine E. _3_ water F. _1_ grapefruit

Learning Check AB2 Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H+ in aqueous solutions

Solution AB2 Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH- in aqueous solutions _B_ 3. Chalky taste A, B 4. Is an electrolyte _A_ 5. Produces H+ in aqueous solutions

Learning Check AB3 Acid, Base Name or Salt CaCl2 ______ _________________ KOH ______ _________________ Ba(OH)2 ______ _________________ HBr ______ _________________ H2SO4 ______ __________________

Solution AB3 Acid, Base Name or Salt CaCl2 salt calcium chloride KOH base potassiuim hydroxide Ba(OH)2 base barium hydroxide HBr acid hydrobromic acid H2SO4 acid sulfuric acid