Acids And Bases

1. Acids AndBases

2. Section 19.1Acid-Base Theories • OBJECTIVES: • Define the properties of acids and bases.

3. Section 19.1Acid-Base Theories • OBJECTIVES: • Compare and contrast acids and bases as defined by the theoriesof: a) Arrhenius, b) Brønsted-Lowry, and c) Lewis.

4. Where can acids be found? Sodas Stomach Vinegar Citrus fruits Where can bases be found? Soap Drano Antacid tablets Windex detergent Class question

5. Properties of Acids • Taste sour • React with bases • Litmus paper test – turn blue litmus paper red • Electrolytic – conduct electricity • Can be strong or weak electrolytes in aqueous solution

6. Properties of Acids • They have a pH of less than 7 (more on this concept of pH in a later lesson) • How do you know if a chemical is an acid? • It usually starts with Hydrogen. • HCl, H2SO4, HNO3, etc. (but not water!)

7. Acids Affect Indicators, by changing their color Blue litmus paper turns red in contact with an acid (and red paper stays red).

8. Acids have a pH lessthan 7

9. Properties of Bases • Taste bitter • Feels slippery • React with acids • Litmus paper test – turn red litmus paper blue • electrolytic

10. Bases Affect Indicators Red litmus paper turns blue in contact with a base (and blue paper stays blue). Phenolphthalein turns purple in a base.

11. Bases have a pH greaterthan 7

12. Acid Nomenclature

13. Nomenclature of Acids • Acids are composed of a(n) ________________ followed by a(n) _______ Hydrogen ion (H+) anion H+ + Cl1- HCl Ex: H+ + SO42- H2SO4

14. Binary AcidsH+ + anion • H+ + anion with –ide ending  acid name is __________________ HCl anion? _______ acid name ________________ Hydro _____ic acid chloride Hydrochloric acid

15. Binary AcidsH+ + anion • H+ + anion with –ide ending  acid name is __________________ HF anion? _______ acid name ________________ Hydro _____ic acid fluoride Hydrofluoric acid

16. OxyacidsH+ + anion • H+ + anion with –ate ending  acid name is __________________ HNO3 anion? _______ acid name ________________ _____ic acid nitrate nitric acid

17. OxyacidsH+ + anion • H+ + anion with –ate ending  acid name is __________________ H2SO4 anion? _______ acid name ________________ _____ic acid sulfate sulfuric acid

18. OxyacidsH+ + anion • H+ + anion with –ite ending  acid name is __________________ HNO2 anion? _______ acid name ________________ _____ous acid nitrite nitrous acid

19. OxyacidsH+ + anion • H+ + anion with –ite ending  acid name is __________________ HClO2 anion? _______ acid name ________________ _____ous acid chlorite chlorous acid

20. Writing acid formulas • Hydrobromic acid anion? ___________ formula ______ • Acetic acid anion? ___________ formula ______ • Nitrous acid anion? ___________ formula ______ HBr Bromide (Br1-) HC2H3O2 acetate(C2H3O21-) HNO2 nitrite (NO21-)

21. Base Nomenclature

22. Nomenclature of Bases • Bases are composed of a(n) _______ followed by a(n) ________________ cation hydroxide (OH1-)

23. Writing Base Names • Rule: name the cation and add “hydroxide” • NaOH • Mg(OH)2 • Fe(OH)3 sodium hydroxide magnesium hydroxide Iron (III) hydroxide Memorize: NH3 = ammonia

24. Writing base formulas • potassium hydroxide cation? ______ formula ______ • Calcium hydroxide cation? ______ formula ______ • Aluminum hydroxide cation? ______ formula ______ KOH K+ Ca(OH)2 Ca2+ Al(OH)3 Al3+

25. Ions In Solution • Why are some solutions acidic, basic, or neutral? It depends on number of H+ and OH- ions present.

26. Ions In Solution • Acidic solution – contain more H+ ions than OH- ions 4000 H+ and 0 OH- is acidic 1000 H+ and 500 OH- is acidic 5 H+ and 3 OH- is acidic

27. Ions In Solution • Basic Solution – contain more OH- ions than H+ ions 4000 OH- and 0 H+ is basic 1000 OH- and 500 H+ is basic 5 OH- and 3 H+ is basic

28. Ions In Solution • Neutral Solution – equal amounts of H+ and OH- ions 4000 OH- and 4000 H+ is neutral 1000 OH- and 1000 H+ is neutral 5 OH- and 5 H+ is neutral

29. Self Ionization of Water • Proper ionization H2O + H2O  H3O+ + OH- hydronium ion H O +  O + O H H H H H O H H

30. Self Ionization of Water • simplified version H2O  H+ + OH-

31. Acid-Base Theories

32. Types of Acids/Bases • Arrhenius Model • Bronsted-Lowry Model • Lewis Model

33. Svante Arrhenius • He was a Swedish chemist (1859-1927), and a Nobel prize winner in chemistry (1903) • one of the first chemists to explain the chemical theory of the behavior of acids and bases • Dr. Hubert Alyea (professor emeritus at Princeton University) was the last graduate student of Arrhenius.

34. Hubert N. Alyea (1903-1996)

35. Svante Arrhenius (1859-1927)

36. Arrhenius Model of Acids and Bases • Arrhenius Acids • Defn: contain H+ and ionizes to form H+ • Examples HCl  HNO3  makes solution ACIDIC H+ + Cl- H+ + NO3-

37. Arrhenius Model of Acids and Bases • Arrhenius Bases • Defn: • contain OH- and ionizes to produce OH- ions • Examples NaOH  Ca(OH)2  makes solution BASIC Na+ + OH- Ca2+ + 2 OH-

38. Flaw with Arrhenius model • Not all bases contain hydroxide • Ex: ammonia (NH3) is basic • According to Arrhenius, since ammonia can NOT produce OH- it is NOT a base • Therefore a new type of acid/base must be determined

39. Gilbert Lewis (1875-1946)

40. Lewis Acids and Bases • Gilbert Lewis focused on the donation or acceptance of a pair of electrons during a reaction • Most general of all 3 definitions; acids don’t even need hydrogen!

41. Lewis Model • Lewis acid • an atom, ion, or molecule that accepts an electron pair to form a covalent bond • Lewis base • An atom, ion, or molecule that donates an electron pair to form a covalent bond

42. Lewis Model • Lewis acid-base reaction • The formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor

43. Example • Acidsare electron pair acceptors. • Bases are electron pair donors. Lewis base Lewis acid

44. Johannes Brønsted Thomas Lowry (1879-1947) (1874-1936) Denmark England

45. Bronsted-Lowry Model • Bronsted-Lowry Acid • Defn: proton/H+donor • can give H+ to another species • Bronsted-Lowry Base • Defn: proton/H+acceptor • can take H+ from another species **Acids and bases always come in pairs.**

46. Bronsted-Lowry Model • REMEMBER!!!! REMEMBER!!!! acids donate, bases accept protons Ashley does boys always

47. Bronsted-Lowry Model • Examples HCl + H2O  Cl- + H3O+ What is happening here? Acid (donates proton) Base (accepts proton) Which is the acid? base? Water is a base—when the HCl gives up the proton, water accepts it to form the hydronium ion HCl is an acid — when it dissolves in water, it gives it’s proton to water.

48. Bronsted-Lowry Model • Examples NH3 + H2O  NH4+ + OH- What is happening here? Base (accepts proton) Acid (donates proton) Which is the acid? base?

49. Why Ammonia is a Base • Ammonia can be explained as a base by using Brønsted-Lowry: NH3(aq) + H2O(l)↔ NH41+(aq) + OH1-(aq) Ammonia is the hydrogen ion acceptor (base), and water is the hydrogen ion donor (acid).

50. Conjugate Acid/Base Pairs • Conjugate acid – new species produced when base gains H+ ion • Conjugate base – new species produced when acid donates H+ ion Thus, a conjugate acid-base pair is related by the loss or gain of a single hydrogen ion.