PowerPoint Presentation

Unit 16Section 1 Properties of Acids and Bases

Section 2 Determining the Acidity of a Solution

Section 3 Titrations and BuffersAcids and Bases To learn about two models of acids and bases To understand the relationship of conjugate acid-base pairs To understand the concept of acid strength To understand the relationship between acid strength and the strength of the conjugate base To learn about the ionization of water Objectives Section 1 Properties of Acids and BasesAcids and Bases 2Acids and Bases Acid produces hydrogen ions in aqueous solution Base produces hydroxide ions in aqueous solution The Arrhenius ModelAcids and Bases 3Acids and Bases Acid proton donor Base proton acceptor The general reaction for an acid dissolving in water is The Bronsted-Lowry Model

Acids and Bases 4Acids and Bases The Bronsted-Lowry Model Conjugate acid-base pair

Acids and Bases 5Acids and Bases The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. Forms hydronium ion (H3O+)

Acids and Bases 6Acid Strength Strong acid completely ionized or completely dissociated

Acids and Bases 7Acid Strength Weak acid most of the acid molecules remain intact

Acids and Bases 8Acid Strength A strong acid contains a relatively weak conjugate base.

Acids and Bases 9Acid Strength Common strong acids are Sulfuric acid, H2SO4 Hydrochloric acid, HCl Nitric acid, HNO3 Perchloric acid, HClO4 Acids and Bases 10Acid Strength Oxyacid acidic proton is attached to an oxygen atom Typically a weak acid Organic acid have a carbon atom backbone and commonly contain the carboxyl group

Acids and Bases 11Acid Strength

Acids and Bases 12Water as an Acid and a Base Water is amphoteric it can behave as either an acid or as a base Ionization of water Concentration of hydronium and hydroxide are equal

Acids and Bases 13Water as an Acid and a Base Product of [H3O+] and [OH] is always constant.

Acids and Bases 14Water as an Acid and a Base

Acids and Bases 15To understand pH and pOH To learn to find pH and pOH for various solutions To use a calculator to find pH To learn methods for measuring pH of a solution To learn to calculate the pH of strong acids Objectives Section 2 Determining the Acidity of a SolutionAcids and Bases 16The pH Scale The p scale is used to express small numbers.pH = log [H+]

Acids and Bases 17The pH Scale

Acids and Bases 18The pH Scale Because the pH scale is a log scale based on 10, the pH changes by 1 for every power of 10 change in the [H+].

Acids and Bases 19The pH Scale

Acids and Bases 20The pH Scale pOH scale pOH = log [OH] pH + pOH = 14.00Acids and Bases 21The pH Scale

Acids and Bases 22Measuring pH Indicators substances that exhibit different colors in acidic and basic solutions In an acid solution the indicator will be in the HIn form. In a basic solution the indicator will be in the In form.

Acids and Bases 23Measuring pH Other methods Indicator paper pH meter Acids and Bases 24C. Calculating the pH of Strong Acid Solutions Determine the [H+]. pH = log[H+] Acids and Bases 25 To learn about acid-base titrations To understand the general characteristics of buffered solutionsObjectives Section 3 Titrations and BuffersAcids and Bases 26Acid-Base Titrations Titration delivering a measured volume of a solution of known concentration into the solution being analyzed Titrant a standard solution Buret device used for accurate measurement of the delivery of a liquid Stoichiometric point (equivalence point) when just enough titrant has been added to react with all of the solution being analyzed Acids and Bases 27Acid-Base Titrations Titration curve (pH curve) plot of the data (pH vs volume) for a titration

Acids and Bases 28Buffered Solutions Buffered solution resists a change in its pH when either and acid or a base has been addedPresence of a weak acid and its conjugate base buffers the solution Acids and Bases 29Buffered Solutions

Acids and Bases 30