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Acids and Bases

Acids and Bases. Chapter 10. Acid-Base Theories. Properties of Acids and Bases Arrhenius Acid-Base Theory Br Ønsted -Lowry Acid-Base Theory strong and weak acids and bases acid nomenclature review. Properties of Acids and Bases. Acids taste sour conduct electricity in aqueous solution

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Acids and Bases

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  1. Acids and Bases Chapter 10

  2. Acid-Base Theories • Properties of Acids and Bases • Arrhenius Acid-Base Theory • BrØnsted-Lowry Acid-Base Theory • strong and weak acids and bases • acid nomenclature review

  3. Properties of Acids and Bases Acids • taste sour • conduct electricity in aqueous solution • turn litmus red • react with carbonates to produce CO2(g) • react with active metals to produce H2(g)

  4. Examples of Acids • citric acid • ascorbic acid • lactic acid • carbonic acid • muriatic acid (aka: hydrochloric acid)

  5. Bases • feel slippery • taste bitter • turn litmus blue • do not react with carbonates or with active metals

  6. Examples of Bases • drain cleaner and oven cleaner (NaOH) • baking soda (NaHCO3) • washing soda (Na2CO3) • glass cleaner (ammonia, NH3(aq)) • Na3PO4 (aka “TSP”)

  7. Arrhenius Theory of Acids and Bases Acids ionize in water to produce hydronium, H3O+(aq), ions. eg. This is an ionization reaction. HCl(g) + H2O(l)  H3O+(aq) + Cl−(aq) HCl(aq)

  8. writes this equation as: HCl(g)  H+(aq) + Cl−(aq) NB. The H+ ion does not exist as such in aq solution. The hydronium ion is a hydrated proton, H+.

  9. some fine print . . . Some texts, like ours, abbreviate the hydronium ion, H3O+, as H+, called a hydrogen ion. This is inaccurate! H+ is a bare proton—which cannot exist in water. Take a look . . .

  10. the aqueous hydronium ion: What is the geometry of the hydronium ion? pyramidal

  11. Bases dissociate in water to produce one or more hydroxide, OH–(aq), ions. eg. This is a dissociation reaction. Na(OH)(s)  Na+(aq) + OH–(aq) Ba(OH)2(s)  Ba2+(aq) + 2OH–(aq)

  12. Limitations of the Arrhenius Theory • restricted to acids & bases in aq solution • doesn’t explain behaviour of all acids or bases • doesn’t explain certain types of neutralization reactions NH3(g) + HCl(g)  NH4Cl(s)

  13. BrØnsted-Lowry Acid-Base Theory Acid: proton (H+) donor Base: proton (H+) acceptor not restricted to aq. solutions Explains NH3(g) + HCl(g)  NH4Cl(s) (note that N in NH3 has a lone pair of e-s)

  14. In order to qualify as a B-L acid, a compound must contain _____________. (hydrogen) In order to qualify as a B-L base, a compound must contain ______________ . (lone pair of e–s— or a negative charge)

  15. Some B-L Acids & Bases HCl(g) + H2O(l) H3O+(aq) + Cl−(aq) B-L acidB-L base NH3(aq) + H2O(l) NH4+(aq) + OH−(aq) B-L base B-L acid Water can act as either a B-L acid or base; water is amphiprotic.

  16. Conjugate Acid-Base Pairs HCl(g) + H2O(l) H3O+(aq) + Cl−(aq) B-L acidB-L base conj acidconj base NH3(aq) + H2O(l) NH4+(aq) + OH−(aq) B-L base B-L acidconj acidconj base

  17. How are conjugate acid-base pairs related? By the transfer of a proton. (Look again at previous slide.)

  18. Identify conjugate acid-base pairs: HCN(aq) + H2O(l) H3O+(aq) + CN−(aq) acidbasec acidc base H2PO4−(aq) + OH−(aq)  HPO42−(aq) + H2O(l) acidbasec basec acid

  19. Strong Acids & Bases A strong acid ionizes 100% in aq soln. eg. HCl(aq) + H2O(l)  H3O+(aq) + Cl−(aq) HClO4(aq) + H2O(l)  H3O+(aq) + ClO4−(aq) 100% rxn indicated by the “”

  20. The “Big Seven” Strong Acids HCl(aq) hydrochloric acid HBr(aq) hydrobromic acid HI(aq) hydriodic acid HClO4(aq) perchloricacid HClO3(aq) chloric acid HNO3(aq) nitric acid 1 mol/L of these ↑ acids = 1 mol/L H3O+(aq) H2SO4(aq) sulfuric acid a diprotic acid1 mol/L acid>1 mol/L H3O+

  21. Review of Acid Nomenclature on the next three slides—taken from nomenclature powerpoint

  22. How does the name of each acid correlate to ending of anion name? HCl(aq) Cl-, chloride hydrochloricacid H2SO4(aq) SO42-, sulfate sulfuricacid HNO2(aq) NO2-, nitrite nitrousacid

  23. Ending of anion name of aciddetermines name of acid 1. anion ends in “-ide” hydro_____ic acid [hydrobromicacid, HBr(aq), Br-, bromide] 2. anion ends in “-ate” _______ic acid [phosphoricacid, H3PO4(aq), PO43-, phosphate] 3. anion ends in “ite” _______ous acid [nitrousacid, HNO2(aq), NO2-, nitrite]

  24. Examples of acids formulaname HClO2(aq) _______________ chlorous acid _______________ acetic (ethanoic) acid HC2H3O2(aq) H3PO3(aq) _______________ phosphorous acid _______________ carbonic acid H2CO3(aq)

  25. Strong Bases Strong Bases dissociate 100% in aq soln. Include the soluble ionic hydroxides of alkali metalsalkali earth metals LiOHSr(OH)2 NaOHBa(OH)2 KOHCa(OH)2 low solubility Mg(OH)2

  26. These ionic hydroxides dissociate in water 100%: NaOH(s)  Na+(aq) + OH−(aq) Ba(OH)2  Ba2+(aq) + 2OH−(aq)

  27. Concentrated vs Dilute Acids/Bases Concentrated acids/bases: lots of mol/L eg H2SO4 5 mol/L Dilute acids/bases: few mol/L, say 0.1 mol/L

  28. Describe each of the following acids as strong/weak and dilute/conc 1. 0.10 mol/L HNO3(aq) a dilute, strong acid • 5% (m/v) CH3COOH(aq) a dilute, weak acid 3. 10 mol/L H2SO4(aq) a concentrated, strong acid

  29. Weak Acids and Bases Ionize less that 100%—usually much less—in aq solution. (eg acetic acid, CH3COOH) + H2O H3O+(aq) + CH3CO2−(aq) represents < 100% yield (an equilibrium)

  30. Example of weak base, ammonia: NH3(aq) + H2O(l) NH4+(aq) + OH−(aq) • ammonia ionizes only a few % • what does this say about the yield of this rxn? (only a few %) Now indicate conj. acid-base pairs above.

  31. NH3(aq) + H2O(l) NH4+(aq) + OH−(aq) wk baseacid c. acid c. base

  32. Homework 10.1 LC # 1 – 12 RQ # 1 - 16

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