Chemistry of Acids and Bases - Chemistry 112 Laboratory:...

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Chemistry of Acids and BasesThe chemistry of acids and bases is an area of fundamental importance inchemistry. In this experiment you will study acid-base equilibria by deter-mining the pH of a number of acids and bases and their mixtures and by per-forming a pH titration. In particular, the aims of this experiment are:1.To demonstrate that only a very small concentration of H3O+and OH-aregenerated in solutions of weak acids and bases, respectively.2.To demonstrate the acid-base properties of salts of weak acids and bases.3.To prove the buffering action of a solution of a weak acid and its salt or ofa weak base and its salt.4.To demonstrate the pH changes occurring in the course of the titration ofa weak polyprotic acid with a strong base and how to determine the valuesfor the acid.5.To demonstrate the connection between the pH of a solution and the colorof an acid-base indicator.Introduction to Acids and Bases1.Acidic and Basic SubstancesAcids are molecules or ions that act as proton (H+) donors. As illustrated inFigure 1, the acid can be a neutral molecule, a cation, or an anion. The speciesthat results from the loss of the H+ion by the acid is called its conjugate base.Thus, the conjugate base will always be one unit more negative in its chargethan the acid.AcidConjugate Base + H+Bases are the opposite of acids: bases are proton acceptors. This means thatthe conjugate acid of a base will be more positively charged than the base.Chemistry 112 Laboratory: Chemistry of Acids & BasesPage 43This experiment isbased on experimentsdone in general chem-istry at the Universityof Auckland inAuckland, New Zealand.We thank Dr. SheilaWoodgate for sharingthis information.A complete discussionof acid-base chemistryis given in Chapters 17and 18 ofChemistry &Chemical Reactivity.CH3CO2HH2ONH4+H3O+H2PO4-ACIDacetic acidwaterammoniumionhydroniumiondihydrogenphosphate ionBASECH3CO2-acetate ionOH-hydroxideionNH3ammoniaH2OwaterHPO42-hydrogenphosphate ion+H+-H++H+-H++H+-H++H+-H++H+-H+Neutral AcidCationic AcidAnionic AcidAnionic BaseNeutral BaseDianion BaseFigure 1Some repre-sentative acids andbases.NOTE: If you downloadthis experiment fromthe Net, the doublearrows font used foran equilibrium processdoes not print.

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Term
Fall
Professor
Staff
Tags
Chemistry, Bases, pH, Chemistry of Acids Bases

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