chapter 15 notes

chapter 15 notes - Chapter 15 Acids Bases and Acid-Base...

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©2010 Donald L. Siegel, All Rights Reserved Chapter 15 Chapter 15 Acids, Bases and Acid-Base Equilibria
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©2010 Donald L. Siegel, All Rights Reserved What are acids and bases? What are acids and bases? W Arrhenius Acids produce H + in solution Bases produce OH - in solution Too limited W Brønsted-Lowery Acid: proton donor Base: proton acceptor Still limited W Lewis Acids and bases Acid: electron pair acceptor Base: electron pair donor Too broad?
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©2010 Donald L. Siegel, All Rights Reserved Conjugate Conjugate acd acd - - base pairs base pairs W Under the Brønsted-Lowery model, each acid has a conjugate pair base (other side of reaction) W Example NH 3 (aq) + H 2 O( l ) NH 4 + (aq) + OH - (aq) Base Acid Conj. Acid Conj. Base
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©2010 Donald L. Siegel, All Rights Reserved K K a a W Acids dissociate in water, to some extent HA(aq) H + (aq) + A - (aq) [ ][ ] [ ] HA A H K a + =
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©2010 Donald L. Siegel, All Rights Reserved Acid Strength Acid Strength W Strong acids dissociate more than weak ones K a larger for stronger acids, reaction lies to the right Very strong acids dissociate completely Weak acids, equilbrium lies to the left W The stronger the acid, the weaker the conjugate base The conjugate base of a weak acid is a weak base. The conjugate base of a strong acid is a very weak base.
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©2010 Donald L. Siegel, All Rights Reserved Types of acids Types of acids W Oxoacids Acidic H attached to O (except 1 in H 3 PO 3 ) Several are strong W Organic acids Contain carboxylic acid group COOH R C O O H
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©2010 Donald L. Siegel, All Rights Reserved Autoionization Autoionization of water of water W Water can act as either an acid or a base. W To be an acid, it must be a stronger acid than water W The reaction against which we measure is H 2 O( l ) H + (aq) +OH - (aq) H 2 O + H 2 O H 3 O + + OH - acid base acid base K w = [H + ][OH - ] = 1 × 10 -14 at 25 ° C Pure water at 25 ° C, [H + ] = [OH - ] =1 × 10 -7 M
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©2010 Donald L. Siegel, All Rights Reserved pH pH W We are often dealing with weak acids W Even strong acids, [H + ] is frequently <0.001M W People are more comfortable with numbers between 1-10 W Express [H + ] as a –log, called pH potenz hydrogen -log 10 [H + ] pAnything
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©2010 Donald L. Siegel, All Rights Reserved
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