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Chapter 16 Acids and Bases Ionization of Water The pH Scale 7-4.

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Presentation on theme: "Chapter 16 Acids and Bases Ionization of Water The pH Scale 7-4."— Presentation transcript:

1 Chapter 16 Acids and Bases Ionization of Water The pH Scale 7-4

2 Measuring pH Why measure pH? –Everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc. Sometimes we can use indicators, other times we might need a pH meter

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4 pH of Some Common Acids gastric juice1.0 lemon juice2.3 vinegar2.8 orange juice3.5 coffee5.0 milk6.6

5 pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4 milk of magnesia10.6 household ammonia 11.0

6 Calculating pH, pOH pH = -log 10 [H 3 O + ] pOH = -log 10 [OH - ] Relationship between pH and pOH pH + pOH = 14 Finding [H 3 O + ], [OH - ] from pH, pOH [H 3 O + ] = 10 -pH [OH - ] = 10 -pOH

7 In pure water, [H 3 O + ] = [OH - ] = 1  10 –7 Kw = 1  10 –14 pHpOH [H + ][OH - ] pH + pOH = 14 pOH = -log[OH - ]pH = -log[H + ] [H + ][OH - ] = 1.0 

8 pH + pOH = 14

9 Ionization of Water Occasionally, in water, a H + is transferred between H 2 O molecules H : O : + : O : H H : O : H + + : O : H H H H water molecules hydronium hydroxide ion (+) ion (-)

10 Pure Water is Neutral Pure water contains small, but equal amounts of ions: H 3 O + and OH - H 2 O + H 2 O H 3 O + + OH - hydronium hydroxide ion ion 1 x M H3O+H3O+ OH -

11 Ion Product of Water K w [ ] = Molar concentration K w = [ H 3 O + ] [ OH - ] = [ 1 x ][ 1 x ] = 1 x

12 Acids Increase H + HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) More [H 3 O + ] than water > 1 x M As H 3 O + increases, OH - decreases [H 3 O + ] > [OH - ]

13 Bases Increase the hydroxide ions (OH - ) H 2 O NaOH (s) Na + (aq) + OH - (aq) More [OH - ] than water, [OH - ] > 1 x M When OH - increases, H 3 O + decreases [OH  ] > [H 3 O + ]

14 Using K w The [OH - ] of a solution is 1.0 x M. What is the [H 3 O + ]? K w = [H 3 O + ] [OH - ]= 1.0 x [H 3 O + ] =1.0 x [OH - ] [H 3 O + ] = 1.0 x = 1.0 x M 1.0 x

15 Learning Check pH The [H 3 O + ] of lemon juice is 3.0 x M. What is the [OH - ] of the solution? K w = [H 3 O + ] [OH - ]= 1.0 x [OH - ] =1.0 x [H 3 O + ] [OH - ] = 1.0 x = 3.3 x M 3.0 x

16 pH The [H 3 O + ] of lemon juice is 9.0 x M. What is the [OH - ]? [OH - ] = 1.0 x = 1.1 x M 9.0 x

17 The [H 3 O + ] is 4.0 x M. What is the [OH - ]? 1.0 x x Enter 1.0 EE +/- 14  4.0 EE +/- 5 = 2.5 x

18 Solution pH B.The [H 3 O + ] when [OH - ] of 5 x M K w = [H 3 O + ][OH - ] = 1.0 x [H 3 O + ] = 1.0 x = 2 x x

19 pH Indicates the acidity [H 3 O + ] of the solution pH = - log [H 3 O + ] From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)

20 In the expression for [H 3 O + ] 1 x 10 -exponent the exponent = pH [H 3 O + ] = 1 x 10 -pH M pH

21 pH Range Neutral [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] Acidic Basic

22 pH A. The [H 3 O + ] of tomato juice is 1 x M. What is the pH of the solution? answer: 4 pH = - log [ 1 x ] = -(- 4) = 4

23 pH B. The [OH - ] of an ammonia solution is 1 x M. What is the pH of the solution? Answer: 11 [H 3 O + ] = 1 x pH = - log [ 1 x ] = -(- 11) = 11

24 Some [H 3 O + ] and pH [H 3 O + ] pH 1 x M 5 1 x M 9 1 x M 11

25 Solution pH The pH of a soap is 10. What is the [H 3 O + ] of the soap solution? [H 3 O + ] = 1 x 10 -pH M = 1 x M

26 pH on the Calculator [H 3 O + ] is 4.5 x M. What is the pH. pH = 4.5 x EXP(or EE) 6+/- LOG +/- = 5.35

27 Learning Check pH A soap solution has a [H 3 O + ] = 2 x M. What is the pH of the solution?

28 pH A soap solution has a [H 3 O + ] = 2.0 x M. What is the pH of the solution? 2.0 EE 8 +/- LOG +/- = 7.7

29 Learning Check Identify each solution as 1. acidic 2. basic3. neutral A. _____ HCl with a pH = 1.5 B. _____ Pancreatic fluid [H + ] = 1 x M C. _____ Sprite soft drink pH = 3.0 D. _____ pH = 7.0 E. _____ [OH - ] = 3 x M F. _____ [H + ] = 5 x

30 What is the [H 3 O + ] or [OH - ] in each of the following solutions, also state if the solution is neutral, acidic, or basic. a. 1  M OH - b. 1  M OH - c M H + a.1.0 x M b.1.0 x M c.1.0 x M

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