acid-base - J Garcia 2012 1 Introduction Introduction 2 3...

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1/23/2012 1 ACID-BASE TITRATIONS CONCEPTS AND TITRATION CURVES Jonyl L. Garcia Analytical Chemistry 2 for BS Chemistry 1/23/2012 7:27 PM 1 J. Garcia 2012 Introduction Popular method of analysis Relative ease Speed Low-cost 1/23/2012 7:27 PM 2 J. Garcia 2012 Introduction Successful titration Availability of suitable titrant Fast and quantitative reaction Means of estimating equivalence point 1/23/2012 7:27 PM 3 J. Garcia 2012 Solutions and Indicators in Acid-Base Titrations Standard Solution Strong acids: HCl, HClO 4 , H 2 SO 4 Strong bases: NaOH, KOH, Ba(OH) 2 * Never use weak acids and bases as titrants! 1/23/2012 7:27 PM 4 J. Garcia 2012 Solutions and Indicators in Acid-Base Titrations Indicators Is a weak organic acid or a weak organic base whose undissociated form differs in color from its conjugate acid or its conjugate base form (solvatochromic) Indicator pH range: pK a ±1 1/23/2012 7:27 PM 5 J. Garcia 2012 Common Indicators 1/23/2012 7:27 PM J. Garcia 2012 6 Solutions and Indicators in Acid-Base Titrations Titration Errors with Acid/Base Indicators Determinate error Occurs when the pH at which the indicator changes color differs from the pH at the equivalence point. Can be minimized by choosing the indicator careful y or by making blank correction Indeterminate error Originates from the limited ability of the eye to reproducibly distinguish the intermediate color of the indicator Average visual uncertainty: ± 0.5 to ± 1 pH unit 1/23/2012 7:27 PM 7 J. Garcia 2012 Solutions and Indicators in Acid-Base Titrations Variables that Influence the Behavior of Indicators Temperature Ionic strength of the medium Presence of organic solvents
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This note was uploaded on 02/02/2012 for the course CHEM 211 taught by Professor Santos,j during the Spring '11 term at Abu Dhabi University.

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acid-base - J Garcia 2012 1 Introduction Introduction 2 3...

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