Section 16.1 Properties of Acids and Bases 1. To learn about two models of acids and bases 2. To understand the relationship of conjugate acid-base pairs 3. To understand the concept of acid strength 4. To understand the relationship between acid strength and the strength of the conjugate base 5. To learn about the ionization of water Objectives

Section 16.1 Properties of Acids and Bases A. Acids and Bases Acid – produces hydrogen ions in aqueous solution Base – produces hydroxide ions in aqueous solution The Arrhenius Model

Section 16.1 Properties of Acids and Bases A. Acids and Bases Acid – proton donor Base – proton acceptor The general reaction for an acid dissolving in water is The Bronsted-Lowry Model

Section 16.1 Properties of Acids and Bases A. Acids and Bases The Bronsted-Lowry Model Conjugate acid-base pair

Section 16.1 Properties of Acids and Bases A. Acids and Bases The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. Forms hydronium ion (H 3 O + )

Section 16.1 Properties of Acids and Bases B. Acid Strength Strong acid – completely ionized or completely dissociated

Section 16.1 Properties of Acids and Bases B. Acid Strength Weak acid – most of the acid molecules remain intact

Section 16.1 Properties of Acids and Bases B. Acid Strength A strong acid contains a relatively weak conjugate base.

Section 16.1 Properties of Acids and Bases B. Acid Strength Common strong acids are – Sulfuric acid, H 2 SO 4 – Hydrochloric acid, HCl – Nitric acid, HNO 3 – Perchloric acid, HClO 4

Section 16.1 Properties of Acids and Bases B. Acid 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

Section 16.1 Properties of Acids and Bases B. Acid Strength

Section 16.1 Properties of Acids and Bases C. Water 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

Section 16.1 Properties of Acids and Bases C. Water as an Acid and a Base –Product of [H 3 O + ] and [OH  ] is always constant.

Section 16.1 Properties of Acids and Bases C. Water as an Acid and a Base

Section 16.2 Determining the Acidity of a Solution 1.To understand pH and pOH 2.To learn to find pH and pOH for various solutions 3.To use a calculator to find pH 4.To learn methods for measuring pH of a solution 5.To learn to calculate the pH of strong acids Objectives

Section 16.2 Determining the Acidity of a Solution A. The pH Scale The “p scale” is used to express small numbers. pH =  log [H + ]

Section 16.2 Determining the Acidity of a Solution A. The pH Scale

Section 16.2 Determining the Acidity of a Solution A. The 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 + ].

Section 16.2 Determining the Acidity of a Solution A. The pH Scale

Section 16.2 Determining the Acidity of a Solution A. The pH Scale pOH scale pOH =  log [OH  ] pH + pOH = 14.00

Section 16.2 Determining the Acidity of a Solution A. The pH Scale

Section 16.2 Determining the Acidity of a Solution B. Measuring 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.

Section 16.2 Determining the Acidity of a Solution B. Measuring pH Other methods –Indicator paper –pH meter

Section 16.2 Determining the Acidity of a Solution C. Calculating the pH of Strong Acid Solutions Determine the [H + ]. pH =  log[H + ]

Section 16.3 Titrations and Buffers 1. To learn about acid-base titrations 2. To understand the general characteristics of buffered solutions Objectives

Section 16.3 Titrations and Buffers A. Acid-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

Section 16.3 Titrations and Buffers A. Acid-Base Titrations Titration curve (pH curve) – plot of the data (pH vs volume) for a titration

Section 16.3 Titrations and Buffers B. Buffered Solutions Buffered solution – resists a change in its pH when either and acid or a base has been added –Presence of a weak acid and its conjugate base buffers the solution

Section 16.3 Titrations and Buffers B. Buffered Solutions