Modern Chemistry Chapter 15 AcidBase Titration p H

Modern Chemistry Chapter 15 Acid-Base Titration & p. H

Section 1 • self-ionization of water occurs when two water molecules produce a hydronium (H 3 O+) and a hydroxide (OH-) ion 2 H 2 O H 3 O+ + OH- • The ionization constant (Kw) of water is: Kw = [H 3 O+] [OH-] = 1. 0 x 10 -14 M

Acidic, Basic, & Neutral • IF [H 3 O+] > [OH-] then solution is acidic. • IF [H 3 O+] < [OH-] then solution is basic. • IF [H 3 O+] = [OH-] then solution is neutral.

Calculating [H 3 O+] & [OH-] • Since the product of the hydronium and hydroxide ion concentrations is a constant, we can use the following formula to determine these concentrations. [H 3 O+] [OH-] = 1. 0 x 10 -14 M Use this formula to answer problems #1 -4 on page 502 of the textbook.

The p. H Scale • The p. H of a solution is defined as the negative of the common logarithm of the hydronium ion concentration, [H 3 O+]. p. H = -log [H 3 O+] • The p. OH of a solution is defined as the negative of the common logarithm of the hydroxide ion concentration, [OH-]. p. OH = -log [OH-]

p. H & p. OH p. H + p. OH = 14 14 – p. H = p. OH 14 – p. OH = p. H so and See figure 3 on page 503. See table 3 on page 504. See table 4 on page 504. Do problem #1 on page 505. Do problems #1 -4 on page 506. Do problems #1 -4 on page 508.

Cross-Disciplinary Connection • Read the Cross-Disciplinary Connection titled “Liming Streams” on page 510. • Answer both questions at the end of the article.

Section 2 Determining p. H and Titrations • acid-base indicators are compounds whose colors are sensitive to p. H • transition interval is the p. H range over which an indicator changes color • a p. H meter determines the p. H of a solution by measuring the voltage between two electrodes placed in a solution.

Titration • titration is the controlled addition and measurement of the amount of a solution of a known concentration required to react completely with a measured amount of solution of an unknown concentration • equivalence point is the point at which the two solutions used in a titration are present in chemically equivalent amounts • endpoint is the point in a titration at which the indicator changes color • standard solution is the solution that contains a precisely known concentration of solute

Titration • see figure 10 on pages 518 -519 for the steps of a titration • A general equation for the solution of titration problems would be Va. Maeqa = Vb. Mbeqb Va = volume of acid Ma = molarity of acid eqa = #H in formula of acid Vb = volume of base Mb = molarity of base eqb = #OH in formula of base

Titration • Do practice problems #1 -2 on page 521. • Do section review problems #1 -2 on page 521. • Do chapter review problems #6, 8, 9, 12, 13, 24, 25, & 26 on pages 523 -524.

Modern Chemistry Chapter 15 Test Review • 25 multiple choice – – – – definition of self-ionization [H 3 O+] [OH-] = 1 x 10 -14 definition and formula for calculating p. H = -log[H 3 O+] p. H >7 is a base; p. H <7 is an acid; p. H = 7 is neutral p. H range is normally 0 to 14 calculate p. H from [H 3 O+] calculate [H 3 O+] from p. H definitions of indicators, transition interval, titration, neutralization, endpoint, standard solution – acid-base titration monitors p. H – titration problems using Va. Maeqa = Vb. Mbeqb