SCH 4 U 1. What are buffers? Buffers are mixtures of conjugate acid- base pairs that allow a solution to resist changes in pH when acids and/or bases.

Slides:



Advertisements
Similar presentations
Applications of Aqueous Equilibria
Advertisements

Go over Ch Test Summary of this week Questions over the reading Discussion / explanation Homework.
Buffer Capacity Lab.
Chapter 19 - Neutralization
HCO3-(aq) H+(aq) + CO32-(aq)
AQUEOUS EQUILIBRIA AP Chapter 17.
AP Chemistry Unit 11 – Additional Equilibrium Topics Lesson 1 – The Common Ion Effect Book Section: 17.1.
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.
CHAPTER 15: APPLICATIONS OF AQUEOUS EQUILIBRIA Dr. Aimée Tomlinson Chem 1212.
Chapter 16: Aqueous Ionic Equilibria Common Ion Effect Buffer Solutions Titrations Solubility Precipitation Complex Ion Equilibria.
Ch. 16: Aqueous Ionic Equilibrium Dr. Namphol Sinkaset Chem 201: General Chemistry II.
Chapter 17: Additional Aspects of Aqueous Equilibria
Chapter 9 Acids, Bases, & Salts
Buffers: -A buffer solution is that solution that allows solutions to resist large changes in pH upon the addition of limited amounts of acid Or base.
Outline:3/7/07 è Pick up CAPA 15 & 16 - outside è 4 more lectures until Exam 2… Today: è Chapter 18 Buffers Buffer calculations Titrations.
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.
Acids, Bases and Buffers The Br Ø nsted-Lowry definitions of an acid and a base are: Acid: species that donates a proton Base: species that can accept.
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) +
Buffer solution دکتر امید رجبی دانشیار گروه شیمی دارویی شیمی عمومی.
1 Chapter 10 Acids and Bases 10.9 Buffers. 2 When an acid or base is added to water, the pH changes drastically. A buffer solution resists a change in.
Chapter 16 Aqueous Ionic Equilibrium. pH / pOH Calculations Strong acids Strong bases Weak acids Weak bases Salts.
EQUILIBRIUM Part 1 Common Ion Effect. COMMON ION EFFECT Whenever a weak electrolyte and a strong electrolyte share the same solution, the strong electrolyte.
Neutralization, Titration & Concentration. Neutralization For an acid to effectively neutralize a base (or vice versa) the number of moles of acid and.
Chemistry 1011 TOPIC TEXT REFERENCE Acids and Bases
Ch. 15: Applications of Aqueous Equilibria 15.1 Common Ion Effect.
Section 2: Buffered Solutions.  Solutions prepared with common ions have a tendency to resist drastic pH changes even when subjected to the addition.
Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille, Chemistry, 2007 (John Wiley)
Buffers 4/13/2011. Definitions Weak Acids: all proton donors that are in equilibrium Conjugate Bases: the ions that are left over after a weak acid loses.
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.
Additional Aqueous Equilibria CHAPTER 16
12 AP Chemistry Buffers. What is a Buffer? A buffer solution is one, which can absorb additions of acids or bases with only slight changes in pH values.
Titrations of acids and bases. HA + H 2 O H 3 O + + A -
Acids, Bases and Equilibria. Overview Definitions Strong acids pH Water equilibrium Weak acids Buffers Other equilibria LeChatlier’s Principle.
Section 16.3 Titrations and Buffers 1.To know how to neutralize acids and bases (titration) Learning Goal.
Chemistry 2100 Chapters 7 and 8. Chemical kinetics Chemical kinetics: The study of the rates of chemical reactions. –Consider the reaction that takes.
3 Acids, Bases, and Buffers
Aqueous Equilibria © 2009, Prentice-Hall, Inc. Chapter 17 Additional Aspects of Aqueous Equilibria Chemistry, The Central Science, 11th edition Theodore.
Aqueous Equilibria Chapter 15 Additional Aspects of Aqueous Equilibria © 2009, Prentice-Hall, Inc.
Agenda Do Now : 1.write the products of the reaction when the reactants given below undergoes double replacement reaction and balanced the equation:
Acid-Base Equilibria and Solubility Equilibria Chapter 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ACID-BASE EQUILIBRIUM. Arrhenius Theory  Acids – are solutes that produce hydrogen ions H + in aqueous solutions ex. HCl (aq)  H + (aq) + Cl - (aq)
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois Chapter 15 Applications.
Additional Aspects of Aqueous Equilibria. Buffer Solutions solution that resists changes in pH upon addition of small amounts of strong acid or base consists.
Buffers. A buffer is a solution whose pH is resistant to change on the addition of relatively small quantities of an acid or base. Buffers have the ability.
The doctrine about solution. Buffer solution KARAGANDA STATE MEDICAL UNIVERSITY Karaganda 2014y.
Chapter 17 – Equlibria Involving Acids and Bases.
Buffers Chem 12A Mrs. Kay. Buffers help maintain a constant pH. They are able to accept small quantities of acids and bases without drastically changing.
C H E M I S T R Y Chapter 15 Applications of Aqueous Equilibria.
8.3 Bases Similar to weak acids, weak bases react with water to a solution of ions at equilibrium. The general equation is: B(aq) + H2O(l)  HB+(aq) +
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.
Advanced Acid/Base Theory
Acids/Bases Lesson 14 Buffers. Buffer Solutions Buffer solutions are equilibrium systems, which maintain a relatively constant pH when small amounts of.
1081. y = 1.0 x M [OH - ] = 1.0 x M 1082.

Chapter 15 Applications of Aqueous Equilibria
Additional Aspects of Aqueous Equilibria. Roundtable problems P.757: 3, 6, 12, 14, 18, 24, 30, 38, 44, 50, 54, 56, 58, 64, 68, 70, 72, 103.
Applications of Aqueous Equilibria
Acid-Base Equilibria and Solubility Equilibria Chapter 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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.
You’ll find out what buffer solutions are and how they are prepared. Buffer Solutions Definition and Preparation.
Chemistry Chem Olympiad Mini Quiz Buffer Notes Pancake-Ice Cream Sandwich Treat (throughout the class period)
BUFFERS Mixture of an acid and its conjugate base. Buffer solution  resists change in pH when acids or bases are added or when dilution occurs. Mix: A.
ACID-BASE EQUILIBRIA AP CHEM CH 15. The Common Ion Effect The shift in equilibrium that occurs because of the addition of an ion already involved in the.
Acid/base chemistry Buffers Henderson-Hasselbalch equation.
What do they have in common?. And finally ….. BUFFERS.
EXPERIMENT (5) Preparation and Properties of Buffer Solution
12-7 Buffers (Section 16.6)   And you!!!!.
Buffers and titrations
Presentation transcript:

SCH 4 U 1

What are buffers? Buffers are mixtures of conjugate acid- base pairs that allow a solution to resist changes in pH when acids and/or bases are added. 2

When are buffers formed? a) A weak acid is combined with its conjugate base OR b) A weak base is combined with its conjugate acid 3

Example 1 Write the equation to represent the acidic buffer made by combining acetic acid with sodium acetate. In solution, acetic acid does the following: (1)CH 3 COOH + H 2 O  CH 3 COO - + H 3 O + In the same solution, sodium acetate does the following: (2)CH 3 COO - + H 2 O  CH 3 COOH + OH - *Note: Why is Na + is ignored? Notice equation (2) is essentially the reverse of equation (1)! Because it is a neutral ion! 4

(1)CH 3 COOH + H 2 O  CH 3 COO - + H 3 O + (2)CH 3 COO - + H 2 O  CH 3 COOH + OH - This means that in a buffer the following overall reaction takes place: CH 3 COOH + OH -  CH 3 COO - + H 3 O + OR Weak Acid + OH -  Conjugate Base + H 3 O + This general pattern can be used for any buffers. 5

Weak Acid + OH-  Conjugate Base + H 3 O + Using the equation above, we can understand how a buffer works. Consider Le Chatelier’s Principle and determine what will happen in the following situations: A strong acid is added? The equation shifts LEFT to use up the added acid and a new equilibrium is established A strong base is added? The equation shifts RIGHT to use up the added base and a new equilibrium is established 6

Buffer Equations The following can be used to determine ion concentrations in buffers: ACID BUFFER[H 3 O + ] = K a x n A n CB Where n A is moles of weak acid and n CB is moles of conj. base BASE BUFFER[OH - ] = K b x n B n CA Where n B is moles of weak base and n CA is moles of conj. acid 7

Example 2 A 1.00L sample of an aqueous solution contains mol of acetic acid and mol of sodium acetate. Calculate: a) The pH of the solution [H 3 O + ] = K a x n A n CB = 1.8 x (0.200 mol/0.100 mol) = 3.6 x mol/L pH = - log[H 3 O + ] pH = The solution is made up of a weak acid and its conjugate therefore it must be an acidic buffer!

Example 2 cont’d b)The pH of the solution after the addition of 1.00 mL of a 12 M HCl solution First create a chemical equation to represent the buffer Then we can determine what is happening to offset the addition of the acid! 9 WEAK ACID + CH 3 COOH + OH - CONJ BASE CH 3 COO - + H 3 O + I0.200 mol mol0.012 mol C E Note: Any acid added will be used up when equilibrium shifts left! 12 mol/L x L mol mol mol mol0 mol

Example 2 cont’d Now find the new pH using our buffer equation... [H 3 O + ] = K a x n A n CB = 1.8 x (0.212 mol/0.088 mol) = 4.3 x mol/L pH = - log[H 3 O + ] pH = After the addition of HCl the pH shifted slightly and became more acidic, but the shift is only pH units. 10 ↑ very small!

Homework Text page 620 #3 – 9 Read section 8.5 if you need clarification 11