15.1 Acids þ Produce H + ions in water þ Taste sour þ Act Corrosive þ Turn blue litmus paper red
Bases Produce OH - ions in water Taste bitter, chalky Feel soapy, slippery Turn red litmus paper blue
[ ] means concentration or molarity in units (moles / L) [H + ] = mol / L of H + ions In pure water, [H + ] = [OH - ] = same [H + ] > [OH - ], the solution is ???. [H + ] < [OH - ], the solution is ??? Acidic Basic
pH of Some Common Materials SubstancepH Vomit (HCl) ~ 2 Lemon juice2.3 Coffee5.0 Saliva~ 7 Blood 7.4 Milk of Magnesia10.5 ammonia11.7 urine6 most colas Root Beer5.5 SubstancepH Vomit (HCl) ~ 2 Lemon juice2.3 Coffee5.0 Saliva~ 7 Blood 7.4 Milk of Magnesia10.5 ammonia11.7 urine6 most colas Root Beer5.5
Buffers A solution that resists changes in pH when a little acid or base is added to it. So it keeps the pH constant. 1.Buffer systems are very important in body fluids. 2.Blood pH needs to stay around a pH value of 7.4 or you will die.
15.2 Arrhenius Acids and Bases Acids produce H + in aqueous solutions HCl (aq) H + + Cl - Bases produce OH - in aqueous solutions NaOH (aq) Na + + OH -
Strengths of Acids and Bases Strong acids ionize completely (~100%) in water. (learn these: HCl, HNO 3, H 2 SO 4 ) HCl (aq) H + + Cl - Strong bases dissociate completely (~100%) in water to form ions. (learn these: KOH, NaOH) NaOH (aq) Na + + OH -
WEAK ACIDS Weak acids ionize very little (~1 %) in water: (learn these: HF, H 2 CO 3, HC 2 H 3 O 2, H 3 PO 4 ) Ex: HC 2 H 3 O 2 (aq) H + + C 2 H 3 O 2 - –Most do not break apart –only ~ 1 % of the acid has ionized
WEAK BASES Weak bases dissociate very little (~1%) so just a few ions are formed: (learn these: NH 4 OH, Mg(OH) 2 ) Ex: NH 4 OH (aq) NH 4 + (aq) + OH - (aq)
Which is a strong acid? Which is a weak acid? Which is a strong base? A B,C none
Neutralization Reactions In general ACID + BASE SALT + H 2 O HCl(aq) + NaOH (aq) NaCl + H 2 O Salt = ionic compound
2 HNO 3 + Ca(OH) 2 2 H 2 O + Ca(NO 3 ) 2 _________is the Arrhenius acid, and __________ is the Arrhenius base HNO 3 Ca(OH) 2
Strong Acids and Bases Acids: –HCl hydrochloric acid –HNO 3 nitric acid –H 2 SO 4 sulfuric acid Bases: –NaOH sodium hydroxide –KOH potassium hydroxide What does strong mean again??? What ions are produced in water for each??
Draw Pictures of HNO 3, HF, KOH, and Mg(OH) 2 in water on the board
15.3 Bronsted-Lowry Acids - Bases Acid is proton (H + ) donor: (loses H + ) Base is proton (H + ) acceptor: (gains H + ) HCl + NH 3 NH Cl - loses H + gains H + acid base
Summary Buffers keep pH constant Arrhenius acids make H + ions in water Arrhenius bases make OH - ions in water Bronsted-Lowry acids lose H + Bronsted-Lowry bases gain H + Strong acids ionize 100% Weak acids ionize way less Strong bases dissociate 100% Weak bases dissociate way less
Enamel erosion occurs below pH of 5. What are you drinking?
Acidic Beverages Erode Teeth
15.10 Electrolytes 1 ) Strong electrolyte - good conductor of electricity. Chemical completely ionizes in water. (all ions) –soluble ionic compounds, strong acids, strong bases – KBr, HNO 3, KOH, NaCl 2)Nonelectrolyte - non-conductor of electricity. - Covalent compounds (no ions) - H 2 O, CO, C 6 H 12 O 6 3) Weak Electrolyte - poor conductor of electricity. Chemical partly ionizes in water. (few ions) –weak acids, weak bases, insoluble ionic solids –HF, Mg(OH) 2, AgCl, H 2 CO 3
Electrolyte Images Which is strong, weak, non?
Electrolyte & Acid Base Videos NaCl HCl vs acetic acid Strong vs weak base Strong vs weak acid
For Fun Blood pH needs to be between 7.35 and 7.45 Maintained by CO 2 / HCO 3 - buffer system –Breathing can affect change in this system in seconds Acidosis is excess acid. Results in heavy breathing, weakness, headache, coma, and pH < 6.8=death. Alkalosis is excess base. Results in convulsions, muscular weakness, and pH>7.8 = death Partial pressure of CO 2 normal is mmHg High P CO2 means acidosis (lots of CO 2 in blood) Low P CO2 means alkalosis (little CO 2 in blood) Buffer rxn: CO 2 + H 2 O H 2 CO 3 H + + HCO 3 -
Self Test Page 445 Try 1-3, 8, 10 Answers in Appendix J