Sections 17.1-2 Acid-Base Reactions Buffer Solutions Bill Vining SUNY Oneonta.

Slides:

Advertisements

Similar presentations

Buffer This. There are two common kinds of buffer solutions: 1Solutions made from a weak acid plus a soluble ionic salt of the weak acid. 2Solutions made.

Advertisements

Weak Acids & Acid Ionization Constant Majority of acids are weak. Consider a weak monoprotic acid, HA: The equilibrium constant for the ionization would.

Chapter 16: Aqueous Ionic Equilibria Common Ion Effect Buffer Solutions Titrations Solubility Precipitation Complex Ion Equilibria.

Conjugates do not react!!

Acid-Base Reactions Copyright © 1999 by Harcourt Brace & Company All rights reserved. Requests for permission to make copies of any part of the work should.

Buffers. Buffered Solutions. A buffered solution is one that resists a change in its pH when either hydroxide ions or protons (H 3 O + ) are added. Very.

Monoprotic Acid-Base Equilibria Monoprotic Weak Acids Monoprotic Weak Bases Fraction of Dissociation-Association Salts of Weak Acids Buffers.

Acid-Base Equilibria Common Ion Effect in Acids and Bases Buffer Solutions for Controlling pH Buffer Capacity pH-Titration Curves Acid-Base Titration Indicators.

__________________________________________ Class Monday, Oct 11, 2004.

Reactions of Acids & Bases

Aqueous Equilibria © 2009, Prentice-Hall, Inc. The Common-Ion Effect Consider a solution of acetic acid: If acetate ion is added to the solution, Le Châtelier.

Chapter 15 Applications of Aqueous Equilibria. The Common-Ion Effect Common-Ion Effect: The shift in the position of an equilibrium on addition of a substance.

Acid-Base Equilibria pH and pOH Relationship of Conjugate Pair acid-base strength. When acids or bases control pH:  determine K  predict pH When pH controls.

QUESTION: What is the effect on the pH of adding NH 4 Cl to 0.25 M NH 3 (aq)? NH 3 (aq) + H 2 O NH 4 + (aq) + OH - (aq) NH 3 (aq) + H 2 O NH 4 + (aq) +

Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved Solutions of Acids or Bases Containing.

EQUILIBRIUM Part 1 Common Ion Effect. COMMON ION EFFECT Whenever a weak electrolyte and a strong electrolyte share the same solution, the strong electrolyte.

Strong Acid-Base Titrations Chapter 17. Neutralization Reactions Review Generally, when solutions of an acid and a base are combined, the products are.

Buffers A buffer is a solution that is highly resistant to changes in pH when a strong acid or base is added. A buffer solution also has a pH close to.

Section 2: Buffered Solutions.  Solutions prepared with common ions have a tendency to resist drastic pH changes even when subjected to the addition.

Aqueous Equilibria Chapter 15 Applications of Aqueous Equilibria.

Which is the stronger acid? 1.HNO 2 2.HNO 3 Which is the stronger base? 1.NO NO 3 -

Chapter 15 Buffers Titration pH Curves

Acid/Base Chemical Equilibria. The Brønsted Definitions  Brønsted Acid  proton donor  Brønsted Base  proton acceptor  Conjugate acid - base pair.

Part 2 Chapter 17. Salt Solutions We will look at the cation and the anion separately, and then combine the result to determine whether the solution is.

Chapter 19 More about ACID-BASES. Self-Ionization of Water Two water molecules produce a hydronium ion & a hydroxide ion by the transfer of a proton.

1 Ch. 8: Acids and Bases Chem 20 El Camino College.

1 Acid-Base Equilibria and Solubility Equilibria Chapter 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Updates Assignment 06 is due Mon., March 12 (in class) Midterm 2 is Thurs., March 15 and will cover Chapters 16 & 17 –Huggins 10, 7-8pm –For conflicts:

(equimolar amounts of acid and base have reacted)

Weak Acids & Weak Bases. Review Try the next two questions to see what you remember Try the next two questions to see what you remember.

Acid and Base Equilibria Electrolytes Strong Conduct electricity Weak Poor conductors of electricity Nonelectrolytes Do not conduct electricity.

ANALYTICAL CHEMISTRY CHEM 3811 CHAPTER 9 DR. AUGUSTINE OFORI AGYEMAN Assistant professor of chemistry Department of natural sciences Clayton state university.

Chem. 1B – 9/22 Lecture. Announcements I Exam 1 –On Oct. 1 (week from next Thurs.) –Some example exams posted (my last Exam 2 for this class is closest.

Aqueous Equilibria Chapter 17 Additional Aspects of Aqueous Equilibria.

Sections 16.3 – 16.6 Acid-Base Equilibria Bill Vining SUNY Oneonta.

Acid/Base Chemistry Part II CHEM 2124 – General Chemistry II Alfred State College Professor Bensley.

Acid/Base Titration Buffers. Buffers A mixture composed of a weak acid and its conjugate base (acidic buffer) OR weak base and its conjugate acid (basic.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois Chapter 15 Applications.

Strong base neutralizes weak acid Strong acid neutralizes weak base.

Buffers. What Are They? Solutions that resist changes in pH with addition of small amounts of acid or base Require two species: an acid to react with.

Marissa Levy Boyi Zhang Shana Zucker. Arrhenius Acid- An acid is a substance that when dissolved increases H + concentration Base- A base is a substance.

C H E M I S T R Y Chapter 15 Applications of Aqueous Equilibria.

Acid – Base Equilibria Buffer Solutions: –Question: Was the ICE Problem set up needed? –Answer: No. The assumption of x

1 Acid-Base Reactions Chapter Acid-Base Reactions Reactions always go from the stronger A-B pair (larger K) to the weaker A-B pair (smaller K).

Neutralization Of strong acids and bases. Example1 1- How many ml of M H 2 SO 4 are required to neutralize exactly 525 ml of 0.06 M KOH? 2- What.

Acid-Base Equilibria pH and pOH Relationship of Conjugate Pair acid-base strength. When acids or bases control pH:  determine K  predict pH When pH controls.

1081. y = 1.0 x M [OH - ] = 1.0 x M 1082.

Aspects of Aqueous Equilibria. Aspects of Aqueous Equilibria: The Common Ion Effect Recall that salts like sodium acetate are strong electrolytes NaC.

WOLPA/AP CHEMISTRY/CDO Chapter 18 Acid-Base Equilibria.

Unit 6 - Chpt 15 - Acid/Base Equilibria Common Ion Effect Buffers / Buffer Capacity Titration / pH curves Acid / Base Indicators HW set1: Chpt 15 - pg.

General Chemistry II Acid and Base Equilibria Lecture 2

Chapter 15 Applications of Aqueous Equilibria

Aqueous Equilibria The Common-Ion Effect Consider a solution of acetic acid: NaC 2 H 3 O 2 Le Châtelier says the equilibrium will shift to the ______.

BUFFERS SUROVIEC SPRING 2014 Chapter I. Buffer Solutions A. Buffer is a solution that resists a change in pH with the addition of small amounts.

Sections Acids and Bases and pH Bill Vining SUNY Oneonta.

Applications of Aqueous Equilibria

See summary: top of p.778 in textbook

3.6: ACIDS AND BASES … Workbook pgs … Buffered Solutions…

PART A M C V C = M D _______ V D = (1.0 M)(5.0 mL) ___________________ (50.0 mL) = 0.10 M HC 2 H 3 O 2.

The common ion effect is the shift in equilibrium caused by the addition of a compound having an ion in common with one of the products.

Salt Hydrolysis. Salts Ionic compound made up of CATION and ANION Has acidic and basic properties Based on ions produced when salts dissociate No acid/base.

[17.2] Buffers. Buffer: a solution that resists a change in pH The best buffer has large and equal amounts of proton donors (weak acid to neutralize OH.

Obj. finish 17.2, ) The pH range is the range of pH values over which a buffer system works effectively. 2.) It is best to choose an acid with.

Acid Reactions I Acids & Active Metals: Single replacement reactions Active metals (K, Na, Ca, Mg, Al, Zn, Fe, Sn) Produce H 2 Oxidation-reduction reactions.

BUFFER – A solution of about equal amounts of a weak acid and its weak conjugate base A buffer is resistant to changes in pH because it can neutralize.

Which is the stronger acid? 1.HNO 2 2.HNO 3. Which is the stronger base? 1.NO NO 3 -

Other Aspects of Aqueous Equilbria:

Applications of Aqueous Equilibria

Chapter 17 Additional Aspects of Aqueous Equilibria

Presentation transcript:

Sections Acid-Base Reactions Buffer Solutions Bill Vining SUNY Oneonta

Acid-Base Reactions Predict reaction for different combinations of strong and/or weak acids and bases. 1) Extent of Reaction 2) Acid-Base Properties of Products

Extent of Acid-Base Reactions

All acid-base reactions involving a strong acid or a strong base go to completion (100%) strong acid + strong base goes 100% strong acid + weak base goes 100% weak acid + strong base goes 100% weak acid + weak base extent depends on acid and base strengths Key: The stronger the base and the acid, the greater the extent of reaction.

Extent of Acid-Base Reactions weak acid + weak base reaction extent depends on relative strengths. Key: The stronger the base and the acid, the greater the extent of reaction. Acid (Ka)Base (Kb)Extent (%) HF (7.2 x )NH 3 (1.8 x )99.9 H 2 CO 3 (4.2 x )NH 3 (1.8 x )96 HCN (4.0 x )NH 3 (1.8 x )46 H 2 CO 3 (4.2 x )NH 3 (1.8 x )96 H 2 CO 3 (4.2 x )CH 3 CO 2 - (5.6 x )13 H 2 CO 3 (4.2 x )NO 2 - (2.2 x )3 HCN (4.0 x )NO 2 - (2.2 x )0.1

Determining K rxn for Acid-Base Reactions Strong acid + Strong base Full Ionic Equation: Net Ionic Equation:

Determining K rxn for Acid-Base Reactions Strong acid + Weak base Net-Ionic Equation

Determining K rxn for Acid-Base Reactions Weak acid + Strong base Net-Ionic Equation

Determining K rxn for Acid-Base Reactions Weak acid + Weak base Calculation of K

Sections 17.2 Acid-Base Buffer Solutions Bill Vining SUNY Oneonta

Acid-Base Buffer Solutions A buffer solution contains a mixture of a weak acid and a weak base, typically the conjugate base of the weak acid. The important property of a buffer solution is that it experiences a relatively small change in pH when a strong acid or a strong base is added.

How a Buffer Works When a strong acid is added to a buffer, the acid reacts with the conjugate base and is completely consumed. When a strong base is added to a buffer, the base reacts with the weak acid and is completely consumed.

How a Buffer Works CH 3 CO 2 H + NaCH 3 CO 2 Buffer If HCl is added, H 3 O + reacts with CH 3 CO 2 - If NaOH is added, OH - reacts with CH 3 CO 2 H

Identifying Buffer Solutions Key: Solution must contain a weak acid AND a weak base. Usually the acid and base are a conjugate pair M HNO M NaNO M Ba(OH) M BaCl HI M NaI 0.31 M NH 4 Br M NH 3

Predicting Buffer pH: Part 1 ICE Tables What is the pH of a buffer solution that is M NH 4 + and M NH 3 ? K a = 5.6 x NH H 2 O(l)  H 3 O + (aq) + NH 3 (aq) Initial Change Equilib.

Predicting Buffer pH: Part 1 ICE Tables Solve for x and determing pH: NH H 2 O(l)  H 3 O + (aq) + NH 3 (aq) –x x x

Predicting Buffer pH: Part 1 ICE Tables General relationship: Caveat: This is true only for a buffer solution. Not for a solution of just an acid or a base.

Predicting Buffer pH: Part 2 Henderson-Hasselbalch Equation Take –log of both sides: Henderson-Hasselbalch Equation

Predicting Buffer pH: Part 2 Henderson-Hasselbalch Equation What is the pH of a solution of 0.31 M NH 4 Br M NH 3 ? K a (NH 4 + ) = 5.6 x

Predicting pH change of a Buffer Solution Following Addition of a Strong Base Steps: 1. Use Henderson-Hasselbalch equation to determine initial pH 2. Assume strong base reacts completely with weak acid 3. Determine “final” concentrations after reaction 4. Use Henderson-Hasselbalch equation to determine new pH

1. Use Henderson-Hasselbalch equation to determine initial pH 2. Assume strong base reacts completely with weak acid 3. Determine “final” concentrations after reaction 4. Use Henderson-Hasselbalch equation to determine new pH What is the pH change when 16 mL of 2.5 M NaOH is added to 500. mL of a solution containing 0.32 M NH 4 Br M NH 3 ?

1. Use Henderson-Hasselbalch equation to determine initial pH 2. Assume strong base reacts completely with weak acid 3. Determine “final” concentrations after reaction 4. Use Henderson-Hasselbalch equation to determine new pH What is the pH change when 16 mL of 2.5 M NaOH is added to 500. mL of a solution containing 0.32 M NH 4 Br M NH 3 ?

Preparing Buffer Solutions: Two Methods Direct Addition or Acid-Base Reaction Steps: 1. Choose an acid-base pair with pK a near (within 1 unit) desired pH 2. Determine ratio: [weak acid]/[weak base] 3a. Preparation by Direct Addition Determine masses of acid and base to use. 3b. Preparation by Acid-Base Reaction Determine volume of solutions to use.

Preparing a Buffer by Direct Addition Prepare 250 mL of a buffer of pH = 4.32 using one of the acid-base pairs here. The concentration of the weak acid should be M.

Preparing a Buffer by Acid-Base Reaction What volume of 2.00 M NaOH solution should be added to 250. mL of acetic acid solution to create a buffer of pH 4.32?

Preparing a Buffer by Acid-Base Reaction What volume of 2.00 M NaOH solution should be added to 250. mL of acetic acid solution to create a buffer of pH 4.32?