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1 Acids and Bases Chapter 15 Chemistry chapter 15.

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Presentation on theme: "1 Acids and Bases Chapter 15 Chemistry chapter 15."— Presentation transcript:

1 1 Acids and Bases Chapter 15 Chemistry chapter 15

2 2 Overview Many acids are found in foods. They usually taste sour or tart. Bases are found in many household cleaners and some foods. They often taste bitter. Chemistry chapter 15

3 3 Acids Aqueous solutions of acids taste sour. Often corrosive and/or poisonous Acids change the color of acid-base indicators in predictable ways. Acids react with bases to produce salts and water. Some acids undergo single-replacement reactions with active metals to release hydrogen gas. Some acids are electrolytes. Chemistry chapter 15

4 4 Binary acids Contain only two different elements Hydrogen and a more electronegative element Chemistry chapter 15

5 5 Naming binary acids In pure form, they are gases. In aqueous solutions, they are known by their acid names. Always begin with the prefix hydro- Then add the root of the name of the other element Finally, add the suffix - ic Chemistry chapter 15

6 6 Oxyacids An acid that is a compound of hydrogen, oxygen, and a third element, usually a nonmetal. One type of ternary acids (containing three elements). Usually written as one or more hydrogen atoms followed by a polyatomic anion. Names are based on the anion. Chemistry chapter 15

7 7

8 8 Sulfuric Acid The most commonly produced industrial chemical Over 47 million tons made per year in US Uses Petroleum refining Fertilizer manufacturing Battery acid Chemistry chapter 15

9 9 Sulfuric Acid Dehydrating agent Removes water Causes serious burns by attacking organic compounds in skin Chemistry chapter 15

10 10 Nitric Acid Volatile, unstable liquid Becomes more stable when dissolved in water Stains proteins yellow Causes serious burns Has a suffocating odor Used to make explosives, among other things Chemistry chapter 15

11 11 Phosphoric Acid Used to manufacture fertilizers and animal feed When dilute, provides a pleasant, yet sour, taste to beverages. Used as a cleaning agent Used to make detergents Chemistry chapter 15

12 12 Hydrochloric Acid Produced in your stomach Used to “pickle” iron and steel Remove surface impurities Used for cleaning Muriatic acid – weak HCl Used in swimming pools and for cleaning Chemistry chapter 15

13 13 Acetic Acid Pungent-smelling liquid Called glacial acetic acid – freezes at 17 °C. The acid in vinegar Used to manufacture plastics Used in food supplements Used as a fungicide Chemistry chapter 15

14 14 Discuss Logic in the laboratory Page 463 Chemistry chapter 15

15 15 Bases Aqueous solutions taste bitter Often caustic Change the color of indicators in predictable ways Dilute aqueous solutions feel slippery React with acids to produce salts and water Are electrolytes Chemistry chapter 15

16 16 Arrhenius acids Increase the concentration of hydrogen ions (H + ) in aqueous solutions Chemistry chapter 15

17 17 Arrhenius Bases Increase the concentration of hydroxide, OH - ions, in aqueous solutions. Could contain hydroxide and dissociate Could react with water to form hydroxide ions Chemistry chapter 15

18 18 Aqueous acids Ionizable hydrogen atoms Electrolytes Polar molecules – hydrogen gets stolen by water to form hydronium ions. The anion is left alone Chemistry chapter 15

19 19 Strong Acids One that ionizes completely in aqueous solution. Perchloric Hydrochloric Nitric Strong electrolytes Depends on the polarity of the bond with hydrogen and the difficulty of breaking that bond. Chemistry chapter 15

20 20 Weak acids Weak electrolytes Solutions contain hydronium ions, anions, and molecules. Sulfuric Hydrofluoric Chemistry chapter 15

21 21 Organic Acids Contain the carboxyl group – COOH Generally weak acids Chemistry chapter 15

22 22 Solutions of bases Most bases are ionic, so they dissociate in solution. When a base dissociates completely, the solution is alkaline. Li, Na, K, Rb, Cs (alkali metals) Chemistry chapter 15

23 23 Molecular bases Produces a base when it reacts with water. Chemistry chapter 15

24 24 Strong bases Strong electrolytes Depend on the extent to which the base dissociates or adds hydroxide ions to solution. Chemistry chapter 15

25 25 Discuss Section Review on page 462 Chemistry chapter 15

26 26 Brønsted-Lowry Acids Molecules or ions that are proton donors Includes all Arrhenius acids (H+ is a proton) Also includes other substances, like ions Chemistry chapter 15

27 27 Examples HCl + NH 3  NH 4 + + Cl - Brønsted-Lowry, but not Arrhenius No hydrogen or hydronium ions H 2 O + NH 3  NH 4 + + OH - Water can be a Brønsted-Lowry acid Chemistry chapter 15

28 28 Brønsted-Lowry bases Molecules or ions that are proton acceptors HCl + NH 3  NH 4 + + Cl - Most Arrhenius bases are not Brønsted-Lowry bases Since they are ionic compounds, they don’t accept protons Chemistry chapter 15

29 29 Brønsted-Lowry acid-base reaction Protons are transferred from the acid to the base HCl + NH 3  NH 4 + + Cl - Chemistry chapter 15

30 30 Monoprotic acids Can donate only one proton (hydrogen ion) per molecule HClO 4 HCl HNO 3 Chemistry chapter 15

31 31 Polyprotic acids Can donate more than one proton per molecule H 2 SO 4 H 3 PO 4 Lose hydrogen atoms one at a time Diprotic – can donate 2 Triprotic – can donate 3 Chemistry chapter 15

32 32 Lewis acid An atom, ion, or molecule that accepts an electron pair to form a covalent bond Does not have to contain hydrogen Any compound in which the central atom has three valence electrons and forms three covalent bonds can be a Lewis acid by forming a fourth covalent bond. Chemistry chapter 15

33 33 Lewis base An atom, ion, or molecule that donates an electron pair to form a covalent bond Chemistry chapter 15

34 34 Lewis acid-base reaction The formation of one or more covalent bonds between an electron- pair donor and an electron-pair acceptor. Chemistry chapter 15

35 35 Discuss Table 15-5 on page 468 Section Review, page 468 Chemistry chapter 15

36 36 Conjugate base What is left after a Brønsted-Lowry acid gives up a proton. Chemistry chapter 15

37 37 Conjugate acid What is formed when a Brønsted- Lowry base gains a proton Chemistry chapter 15

38 38 Conjugate acid and base strength The stronger an acid, the weaker its conjugate base. The stronger a base, the weaker its conjugate acid. Chemistry chapter 15

39 39 Reaction direction Proton-transfer reactions favor the production of the weaker acid and the weaker base See table 15-6 on page 471 Chemistry chapter 15

40 40 Amphoteric compounds Something that can react as either an acid or a base If reacting with a stronger acid than itself, acts as a base If reacting with a weaker acid, acts as an acid Chemistry chapter 15

41 41 Hydroxyl group Covalently bonded –OH group The more polar the O-H bond, the more acidic the compound is. Hydrogen is attracted away by the water in solution Chemistry chapter 15

42 42 Neutralization Reactions In aqueous solutions, acids and bases react to neutralize each other and form a salt and water. Antacids Baking powder Chemistry chapter 15

43 43 Neutralization If we write the net ionic equation, we get H 3 O + + OH -  2H 2 O Neutralization: the reaction of hydronium and hydroxide ions to make water Chemistry chapter 15

44 44 Acid Rain Many gases produced by industrial processes can dissolve in atmospheric water to produce acids. Leads to acid rain or snow. Acids react with calcium carbonate in marble and erodes it. Chemistry chapter 15

45 45 Discuss Which way do proton-transfer reactions go? How do you know which acid or base is stronger? What is a conjugate acid? What is a conjugate base? Section review #1 on page 475 Chemistry chapter 15

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