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Ch. 15 ACIDS & BASES Ch. 15 ACIDS & BASES GCC CHM 130.

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Presentation on theme: "Ch. 15 ACIDS & BASES Ch. 15 ACIDS & BASES GCC CHM 130."— Presentation transcript:

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2 Ch. 15 ACIDS & BASES Ch. 15 ACIDS & BASES GCC CHM 130

3 15.1 Acids þ Produce H + ions in water þ Taste sour þ Act Corrosive þ Turn blue litmus paper red

4 Bases Produce OH - ions in water Taste bitter, chalky Feel soapy, slippery Turn red litmus paper blue

5 [ ] 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

6 pH Scale Neutral [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] Acidic Basic Strongly acidic Weakly acidic Neutral Weakly basic Strongly basic

7 [H + ] = or 0.1mol/L so pH = 1 [H + ] = mol/L………... pH = [H + ] = mol/L ………... pH = [H + ] = mol/L …………pH = [H + ] = mol/L ……… pH = [H + ] = mol/L.. pH = pH = -log[H + ] or [H + ] =10 -pH

8 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

9 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.

10 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 -

11 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 -

12 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

13 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)

14 Which is a strong acid? Which is a weak acid? Which is a strong base? A B,C none

15 Neutralization Reactions In general ACID + BASE  SALT + H 2 O HCl(aq) + NaOH (aq)  NaCl + H 2 O Salt = ionic compound

16 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

17 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??

18 Draw Pictures of HNO 3, HF, KOH, and Mg(OH) 2 in water on the board

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20 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

21 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

22 Enamel erosion occurs below pH of 5. What are you drinking?

23 Acidic Beverages Erode Teeth

24 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

25 Electrolyte Images Which is strong, weak, non?

26 Electrolyte & Acid Base Videos NaCl HCl vs acetic acid Strong vs weak base Strong vs weak acid

27 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 -

28 Self Test Page 445 Try 1-3, 8, 10 Answers in Appendix J


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