INTRODUCTION TO ACIDS AND BASES

Transcription

1 INTRODUCTION TO ACIDS AND BASES

2 ALIGNED STANDARDS S.C. 912.P.8.11 Relate acidity and basicity to hydronium and hydroxide concentration and ph. S.C.912.N.1.2 Describe and explain what characterizes science and its methods.

3 OBJECTIVES SWBAT distinguish between an Acid and a Base SWBAT describe the relationship between ph & the strength of an acid

4 ESSENTIAL QUESTIONS What is meant by the ph of a substance?

5 Acids Sour taste High concentration of H + ions Conduct electricity good conductor strong acid weak conductor weak acid React with bases to form water and a salt ph of 1-6, the lower the ph the stronger the acid Example lemon juice

6 Bases Also called alkaline bitter taste, soapy feel High Concentration of OH - ions conduct electricity good conductor strong base weak conductor weak base react with acids to form water and a salt ph of 8-14, the higher the ph the stronger the base Example baking soda

7 What are some tests you could do to figure out whether a compound is an acid, abase, or neither?

8 ACID/BASE TESTS Touch / Taste Conductivity test (to see if it is weak or strong) ph paper or ph probe

9 PH SCALE ph below 7 is acidic The closer to 1, the more acidic. ph above 7 is basic The close you get to 14, the more basic. Ranges from 1-14 ph 7 is neutral

10 ACID-BASE VIDEO

11 INDEPENDENT PRACTICE Complete the worksheet and we will grade it in class. If you get done early start on your homework.

12 ACIDS & BASES CALCULATIONS

13 ALIGNED STANDARDS S.C. 912.P.8.11 Relate acidity and basicity to hydronium and hydroxide concentration and ph. S.C.912.N.1.2 Describe and explain what characterizes science and its methods.

14 OBJECTIVES SWBAT compare and contrast the similarities and differences of the 3 main acid-base theories. SWBAT illustrate the dissociation of water and its explain importance. SWBAT recognize common strong/weak acids and bases SWBAT articulate the relationship between ph and H + concentration SWBAT perform calculation involving ph, poh, OH -, and H +

15 ESSENTIAL QUESTIONS What is meant by the ph of a substance?

16 AGENDA Acid Base Theory Arrhenius Acids and Bases Bronsted-Lowry Acids and Bases Lewis Acids and Bases Dissociation of Water Memorizing Common Acids and Bases ph Calculations and Hydrogen Ion Concentrations Relationship between ph and H + concentration Calculating ph Calculating hydronium ion concentration from ph Calculating poh Calculating hydroxide ion concentration from poh The relationship between ph and poh

17 ACIDS HAVE A HIGHER H+ CONCENTRATION LOW ph ACIDIC ARRHENIUS ACIDS AND BASES BASES HAVE A HIGHER OH- CONCENTRATION HIGH ph BASIC

18 BRONSTED-LOWRY ACIDS & BASES Base WHAT IS A PROTON? A PROTON IS COMMONLY USED TO DISCUSS THE DONATION AND ACCEPTANCE OF THE H+ ION.

19 LEWIS ACIDS & LEWIS BASES Electron-pair Donor Electron-pair Acceptor any substance, such as the OH- ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor. any substance, such as the H + ion, that can accept a pair of nonbonding electrons.

20 Acid-Base Theories Acid Base Arrhenius Bronsted-Lowry Lewis Increases the amount of H+ ions in solution Example: HCl (hydrochloric acid) Proton (H+) donor Electron-pair acceptor Increases the amount of OHions in solution Example: NaOH (sodium hydroxide) Proton (H+) acceptor Electron-pair donor

21 DISSOCIATION OF WATER Water has the ability to split into an H + ion and an OH - ions. Water can act as an acid when it donates a H + ion Water can act as a base by accepting an OH - ion.

22 Strong Acids HI Hydroiodic acid HClO 4 perchloric acid HBr hydrobromic acid HCl hydrochloric acid H 2 SO 4 Sulfuric Acid HClO 3 chloric acid COMMON AQUEOUS STRONG ACIDS & STRONG BASES Strong Bases Ca(OH) 2 Calcium hydroxide Sr(OH) Strontium hydroxide BaOH Barium hydroxide NaOH Sodium hydroxide KOH Potassium hydroxide RbOH Rubidium hydroxide CsOH Cesium hydroxide

23 COMMON AQUEOUS WEAK ACIDS & WEAK BASES Weak Acids HSO 4- - Hydrogen sulfate ion H 3 PO 4 Phosphoric acid HF Hydrofluoric acid CH 3 COOH Acetic acid H 2 CO 3 Carbonic acid H 2 S Hydrosulfuric acid HCN - Cyanide HCO hydrogen carbonate ion NH 3 Ammonia Weak Bases C 6 H 5 NH 2 - Aniline

24 As the hydrogen ion concentration increases the ph decreases RELATIONSHIP BETWEEN ph AND HYDROGEN ION CONCENTRATION:

25 If Solution A has a ph of 3 and Solution B has a ph of 2, the first solution is not TWICE as acidic as the second the hydrogen ion concentration has only increased by a factor of. 10

26 THIS MEANS THAT WHEN WE MOVE FROM ONE ph LEVEL TO THE NEXT WE MULTIPLY BY 10. Example: Solution A has a ph of 2 and Solution B has a ph of 6. How much more acidic is solution A than solution B? 10 x 10 x 10 x 10 = ,000 times more ACIDIC

27 IMPORTANT FORMULAS Formula Derived Relationship Explanation ph = -log [H 3 O + ] [poh] = -log (OH - ) [OH-] = 10 -poh Use the hydronium concentration to determine the ph Use the poh to determine hydroxide concentration Use the poh to determine the hydroxide concentration [H + ] = 10 -ph Use the ph to determine the hydronium concentration ph = 14 - poh ph and poh Calculate ph based on H + Concentration Calculate poh based on OH - Concentration Calculate OH - based on poh Concentration Calculate H + based on ph Calculate ph based on poh

28 CALCULATING PH Calculate the ph of a solution with a hydronium concentration of 2.3 x 10-3 M ph = -log [2.3 x 10-3 ] = 2.64 Calculate the ph of a solution with a hydronium concentration of 8.3 x 10-4 M ph = -log [8.3 x 10-4 ] = 3.08 Calculate the ph of a solution with a hydronium concentration of 5.39 x M ph = -log [5.39 x ] = 9.27

29 PUTTING IN THE SCIENTIFIC CALCULATOR Generic Example [(-)] then [log] [ph] [)] [enter] Specific Example [(-)] then [log] [5] [.] [2] [3] [x10 n ] [(-)] [6] [>] [)] [enter] ph = -log [5.23 x 10-6 ]

30 CALCULATING THE H + CONCENTRATION IN A SOLUTION OF A KNOWN PH Calculate the hydrogen ion concentration of a solution with a ph of 4.5 [H + ] = = 3.16 x 10-5 M Calculate the hydrogen ion concentration of a solution with a ph of 6.8 [H + ] = = 1.58 x 10-7 M Calculate the hydrogen ion concentration of a solution with a ph of 12.2 [H + ] = = 6.31 x M

31 Generic Example Specific Example PUTTING IN THE SCIENTIFIC CALCULATOR [2nd] [log] [(-)] [ph] [enter] ph = 10 [-ph]

32 Calculating the poh Calculate the poh concentration of a solution with a OH - concentration of 5.23 x 10-6 M [poh] = -log (5.23 x 10-6 ) = 5.28 Calculate the poh concentration of a solution with a OH - concentration of 8.02 x 10-3 M [poh] = -log (8.02 x 10-3 ) = 2.10 Calculate the poh concentration of a solution with a OH - concentration of 7.36 x 10-8 M [poh] = -log (7.36 x 10-8 ) = 7.13

33 PUTTING IN THE SCIENTIFIC CALCULATOR Generic Example [(-)] then [log] [poh] [)] [enter] Specific Example [(-)] then [log] [2] [.] [3] [x10 n ] [(-)] [3] [>] [)] [enter] ph = -log [2.3 x 10-3 ]

34 CALCULATING THE OH - CONCENTRATION IN A SOLUTION OF A KNOWN poh Calculate the hydroxide ion concentration of a solution with a poh of 5 [OH - ] = 10-5 = 1.00 x 10-5 M Calculate the hydrogen ion concentration of a solution with a ph of 12 [OH - ] = = 1.00 x M Calculate the hydrogen ion concentration of a solution with a ph of 3 [OH - ] = 10-3 = 1000 M

35 Generic Example PUTTING IN THE SCIENTIFIC CALCULATOR [2nd] [log] [(-)] [poh] [enter] Specific Example ph = 10 [poh] [enter]

36 RELATIONSHIP BETWEEN ph AND poh A solution has a poh of What is the ph of this solution? ph = = 2.24 A solution has a poh of What is the ph of this solution? ph = = 4.77 A solution has a ph of What is the ph of this solution? 7.23 = 14 - poh = 6.77 poh =

37 PUTTING IN THE SCIENTIFIC CALCULATOR Given poh Generic Example [14] [-] [poh] [enter] Specific Example [14] [-] [11.76] [enter] Given ph Generic Example [14] [-] [ph] [enter] Specific Example [14] [-] [5.35] [enter]

38 Learning this chart helps make the memorization easier

39 INDEPENDENT PRACTICE Complete the worksheet and we will grade it in class. If you get done early start on your homework.

40 CONJUGATE ACIDS AND CONJUGATE BASE PAIRS

41 ALIGNED STANDARDS S.C. 912.P.8.11 Relate acidity and basicity to hydronium and hydroxide concentration and ph. S.C.912.N.1.2 Describe and explain what characterizes science and its methods.

42 OBJECTIVES SWBAT identify the conjugate acids and conjugate bases of well known acids and bases.

43 ESSENTIAL QUESTIONS What is meant by the ph of a substance?

44 SO FAR WHAT DO WE KNOW? Day 1 What is an acid and a base? What is ph? What is the range of the ph scale? Day 2 What ions common in acids? Bases? How is ph affected by the concentration the H + ions Naming Acids and Bases

45 In this acid-base reaction, An acid, HF, donates H + to form its conjugate base, F. A base, H 2 O, accepts H + to form its conjugate acid, H 3 O+. There are two conjugate acidbase pairs. CONJUGATE ACIDS AND BASES 45

46 46 LEARNING CHECK A. Write the conjugate base of the following. 1. HBr 2. H 2 S 3. H 2 CO 3 B. Write the conjugate acid of the following NO HNO NH 3 3. OH - Br - HS - HCO 3 - NH 4 + H 2 O

47 CONJUGATE ACID-BASE PAIRS 47

48 BRØNSTED-LOWRY ACIDS AND BASES BrØnsted-Lowry Theory acids donate a proton (H + ). bases accept a proton (H + ). 48

49 In the reaction of ammonia and water, NH 3 is the base that accept H +. H 2 O is the acid that donates H +. NH 3, A BRØNSTED-LOWRY BASE 49

50 CONJUGATE ACID-BASE PAIRS EXAMPLE 1 In the reaction of HF and H 2 O, one conjugate acid-base pair is HF/F. the other conjugate acidbase pair is H 2 O/H 3 O +. each pair is related by a loss and gain of H +.

51 In the reaction of NH 3 and H 2 O, one conjugate acid-base pair is NH 3 /NH 4 + the other conjugate acid-base is H 2 O/H 3 O +. CONJUGATE ACID-BASE PAIRS EXAMPLE 2 51

52 52 LEARNING CHECK Identify the sets that contain acid-base conjugate pairs. 1. HNO 2, NO 2 2. H 2 CO 3, CO HCl, ClO 4 4. HS, H 2 S 5. NH 3, NH 4 +

53 53 A. The conjugate base of HCO 3 is 1. CO HCO 3 3. H 2 CO 3 B. The conjugate acid of HCO 3- is 1. CO HCO 3 3. H 2 CO 3 C. The conjugate base of H 2 O is 1. OH 2. H 2 O 3. H 3 O + D. The conjugate acid of H 2 O is 1. OH 2. H 2 O 3. H 3 O + LEARNING CHECK

54 INDEPENDENT PRACTICE Complete the worksheet and we will grade it in class. If you get done early start on your homework.

55 NAMING ACIDS AND BASES

56 Would you use an acid to wash out your eye? Hydrochloric acid causes major damage to even your skin While boric acid is a main ingredient in eye-drop solutions What s the difference?

57 I have two acids 1. Which do you think is stronger? 2. How can we test our prediction? 3. What do you think causes greater conductivity in the stronger acid? DEMO

58 Which is a strong acid? Weak acids/bases only create a small percentage of ions Strong acids/bases create many ions H X X - H + X H H X Cl - Cl - H + H + Cl - Cl - H +

59 Acid/base strength The more ions released in solution, the stronger the acid or base The more ions released in solution, the stronger the acid or base H + H + H + H + Strong H + H + Weak

60 So, why do you think strong acids and bases are good conductors of electricity? HCl solution Strong acids and bases are strong Strong acids and bases are strong electrolytes, electrolytes, because they release many ions because they release many ions

61 CHECK FOR UNDERSTANDING

62 Arrhenius Acids A substance whose water solution contains H + as the only positive ion. Does that mean that all compounds that contain H are acids? H Cl Cl - + H + HCl H + + Cl - Nope! CH 4 does not release H + in water

63 Check for understanding: According to Arrhenius theory of acids, citric acid in oranges and acetic acid in vinegar are classified as acids because their aqueous solutions contain a. hydrogen atoms b. hydrogen ions c. hydroxide atoms d. hydroxide ions

64 Naming acids Binary acids are made of Hydrogen + another element. Hydro + name of element + ic. and acid Ex. HCl: hydrochloric acid. Hydro + name of element ic. Ex. HCl: hydrochloric acid. Ternary acids are more randomly-named: Perchloric Acid Nitric Acid Sulfuric Acid How do we name the compound HBr? hydrobromic acid

65 CHECK FOR UNDERSTANDING Write the formula for the following acids 1. Hydroiodic Acid 2. Hydrochloric Acid 3. Hydrobromic Acid Which of the following is NOT an acid? a. NH 3 b. H 2 SO 4 c. HClO 4 d. HNO 3

66 Arrhenius Bases A solution contains OH A substance whose water solution contains OH - as the - as the only negative ion. H O Na only negative ion. NaOH Na + + OH - - Na + + O H Are all compounds containing OH s bases? Nope! CH 3 OH is not a base.

67 Check for Understanding: When an Arrhenius base is dissolved in H 2 O, the only negative ion present in the solution is a. OH - b. H 3 O - c. H - d. O 2-

68 Naming bases Name of element + hydroxide. Ex. NaOH: sodium hydroxide How do we name the compound KOH? Potassium hydroxide

69 CHECK FOR UNDERSTANDING Fill in the missing boxes Formula NaOH RbOH LiOH Name Potassium Hydroxide Cesium Hydroxide

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71 ACTIVITY: DRAWING ACIDS AND BASES Each pair will be given two substances. For each, use your notes and the chart below to follow each step: 1. Is your substance an acid or a base? 2. What kind of ions will its water solution contain? 3. Draw what will happen to your acid or base when you put it in water. EXAMPLES:

72 INDEPENDENT PRACTICE Complete the worksheet and we will grade it in class. If you get done early start on your homework.