Chapter 14 Acids and Bases

Chapter 14 Table of Contents Copyright © Cengage Learning. All rights reserved The Nature of Acids and Bases 14.2Acid Strength 14.3The pH Scale 14.4Calculating the pH of Strong Acid Solutions 14.5 Calculating the pH of Weak Acid Solutions 14.6Bases 14.7Polyprotic Acids 14.8Acid–Base Properties of Salts 14.9The Effect of Structure on Acid–Base Properties 14.10Acid–Base Properties of Oxides 14.11The Lewis Acid–Base Model 14.12Strategy for Solving Acid–Base Problems: A Summary

Chapter 14 Table of Contents 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

Chapter 14 Table of Contents A. Acids and Bases Acid – produces hydrogen ions H + in aqueous solution: H 2 SO 4 Sulfuric Acid HNO 3 Nitric Acid HCl, HF, HBr, HI: HydroChloric,Fluoric..acid Base – produces hydroxide ions OH - in aqueous solution NaOH Sodium Hydroxide KOH Potassium Hydroxide Mg(OH) 2 The Arrhenius Model

Chapter 14 Table of Contents A. Acids and Bases Acid – proton donor (gives H + ) Base – proton acceptor (takes H + ) The general reaction for an acid dissolving in water is The Bronsted-Lowry Model (1923 Danish/English independent submittals)

Chapter 14 Table of Contents A. Acids and Bases The Bronsted-Lowry Model Acid-base conjugate pairs consist of an acid that donates the H + and the ion it becomes.

Chapter 14 Table of Contents A. Acids and Bases The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. (B-L Base) hydronium ion (H 3 O + ) (Conjugate Acid)

Chapter 14 Table of Contents A. Acids and Bases The Bronsted-Lowry Model can also relate to non-aqueous reactions: NH 3 + HCl  NH Cl - CH 3 COOH + H 2 O  CH 3 COO - + H 3 O + The Arrhenius Model is limited to Aqueous

Chapter 14 Table of Contents A. Acids and Bases Identify the Bronsted-Lowry acid/base conjugate pairs in the following reactions: HCl + H 2 O  Cl - + H 3 O + NH 3 + HCl  NH Cl - CH 3 COOH + H 2 O  CH 3 COO - + H 3 O +

Chapter 14 Table of Contents A. Acids and Bases Identify the Bronsted-Lowry acid/base conjugate pairs in the following reactions: HSO OH -  SO H 2 O SO H 2 O  HSO OH - NH 3 + HNO 3  NH NO 3 -

Chapter 14 Table of Contents A. Acids and Bases The general acid/base pattern is: Acid + Base  salt + water H__ + __OH  ____ + H 2 O HCl + NaOH  NaCl + H 2 O ID the Arrhenius Acid/Base and B-L Pairs…

Chapter 14 Table of Contents B. Acid Strength Strong acid – completely ionized or completely dissociated

Chapter 14 Table of Contents B. Acid Strength Weak acid – low ionization of acids

Chapter 14 Table of Contents B. Acid Strength A strong acid contains a relatively weak conjugate base. HCl + H 2 O  H 3 O + + Cl - Whereas the acid will quickly donate a proton (strong acid), the conjugate base will not quickly accept a proton (weak).

Chapter 14 Table of Contents B. Acid Strength Common strong acids are – Sulfuric acid, H 2 SO 4 – Hydrochloric acid, HCl – Nitric acid, HNO 3 –Are weak acids the same as dilute strong acids?

Chapter 14 Table of Contents B. Acid Strength Oxyacid – acidic proton is attached to an oxygen atom – Typically a weak acid (COOH) Organic acid – have a carbon atom backbone and commonly contain the carboxyl group

Chapter 14 Table of Contents B. Acid Strength

Chapter 14 Table of Contents C. Water as an Acid and a Base Water is amphoteric (amphiprotic) – it can behave as either an acid or as a base Amphiprotic - etymology… ambi-Ringo Starr Ambigram?? ringo_starr.images6.com/ringo_starr.html

Chapter 14 Table of Contents

Chapter 14 Table of Contents Red Rocks Amphitheatre Colorado

Chapter 14 Table of Contents C. Water as an Acid and a Base (Amphiprotic) Ionization of water - ID the B-L conjugate pairs –Concentration of hydronium and hydroxide are equal in pure water

Chapter 14 Table of Contents C. Water as an Acid and a Base –Product of [H 3 O + ] and [OH  ] is always constant in all solutions. –Water is equally both an acid and a base

Chapter 14 Table of Contents C. Water as an Acid and a Base pH range 0.? – 7 7 – 14 7

Chapter 14 Table of Contents 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 6.Work Session: Page 673 # 29 Objectives Review

Chapter 14 Table of Contents 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 and [H+] 4.To learn methods for measuring pH of a solution 5.To learn to calculate the pH of strong acids Objectives

Chapter 14 Table of Contents A. The pH Scale The “p scale” is used to express small numbers. pH =  log [H + ] What is the pH if [H + ] = 1 X ? Calculator practice- do the log function? If [H + ] = 2.3 X ? pH = 4.64 is this acid or base?

Chapter 14 Table of Contents 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 + ].

Chapter 14 Table of Contents A. The pH Scale Calculate the pH given the following concentrations: [H + ] = 1.0 X [H + ] = 1.0 X [H + ] = 3.4 X [H + ] = 2.6 X [H + ] = 2.3 X [H + ] = 1.9 X 10 -6

Chapter 14 Table of Contents A. The pH Scale pOH scale pOH =  log [OH  ] Calculate the pOH if [OH  ] = 1.0 X pOH = 6 remember [H+] [OH  ] = 1.0 X If [OH  ] = 1.0 X 10 -6, then [H + ] = 1.0 X If [OH  ] = 6, then [H + ] = 8 Since pH + pOH = pOH = – pH (shortcut)

Chapter 14 Table of Contents A. The pH Scale Knowing the pH, determine the pOH: [H + ] = 1.0 X pH = 5, pOH = 9 [H + ] = 1.0 X pH = 11, pOH = 3 [H + ] = 3.4 X pH = 3.47, pOH = ? [H + ] = 2.6 X pH = 7.59, pOH = ? [H + ] = 2.3 X pH = 4.64, pOH = ? [H + ] = 1.9 X pH = 5.72, pOH = ?

Chapter 14 Table of Contents A. The pH Scale Can you determine the [H + ] from pH? If pH = 3.98, what is the [H + ] ? Inverse log function….. [H + ] = inverse log (-pH) [H + ] = inverse log (- 3.98) [H + ] = 1.05 X 10 -4

Chapter 14 Table of Contents A. The pH Scale Calculate the [H + ] given the following pH: pH = 5 [H + ] = ? pH = 7[H + ] = ? pH = 10.1 [H + ] = ? pH = 4.5 [H + ] = ? pH = 3.22 [H + ] = ? pH = 9.54 [H + ] = ?

Chapter 14 Table of Contents 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.

Chapter 14 Table of Contents B. Measuring pH –Phenolphthalein color change 8.0 – 9.8

Chapter 14 Table of Contents B. Measuring pH –Bromothymol Blue color change 6.0 – 7.6

Chapter 14 Table of Contents B. Measuring pH –Thymol Blue – tri color!

Chapter 14 Table of Contents B. Measuring pH Other methods –Indicator paper –pH meter –Cabbage juice

Chapter 14 Table of Contents 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 and [H+] 4.To learn methods for measuring pH of a solution 5.To learn to calculate the pH of strong acids 6.Work Session: Page 674 # 41 for 37, 43 Objectives Review

Chapter 14 Table of Contents 1.To learn about acid-base titrations 2.To demonstrate calculations and techniques for titration lab 3.To understand the general characteristics of buffered solutions Objectives

Chapter 14 Table of Contents

Chapter 14 Table of Contents 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

Chapter 14 Table of Contents A. Acid-Base Titrations Titration curve (pH curve) – plot of the data (pH vs volume) for a titration

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + NaOH  NaCl + H 2 O Stoichiometrically, there is a 1 to 1 ratio of H + to OH - ions between HCl and NaOH For this reason, we can use the dilution equation in the form M acid V acid = M base V base to determine the amount of one Molarity solution to completely neutralize a given amount of another Molarity solution

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + NaOH  NaCl + H 2 O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? M acid V acid = M base V base M acid = V acid = M base = V base =

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + NaOH  NaCl + H 2 O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? M acid V acid = M base V base M acid = 1 M V acid = ? M base = 2M V base = 20 ml

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + NaOH  NaCl + H 2 O What volume of 1 M HCl would be required to completely neutralize 20 ml of 2 M NaOH? M acid V acid = M base V base V acid = M base V base M acid V acid = (2M)(20 ml) = 40 ml (1 M)

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + KOH  KCl + H 2 O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of M KOH. M acid V acid = M base V base M acid = V acid = M base = V base =

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + KOH  KCl + H 2 O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of M KOH. M acid V acid = M base V base M acid = 0.30 M V acid = ? M base = M V base = 75.0 ml

Chapter 14 Table of Contents A. Acid-Base Titrations HCl + KOH  KCl + H 2 O Calculate the volume of 0.30 M HCl needed to titrate 75.0 ml of M KOH. M acid V acid = M base V base V acid = M base V base M acid V acid = (0.150M)(75 ml) = 37.5 ml HCl (0.30 M)

Chapter 14 Table of Contents A. Acid-Base Titrations (Lab Prep) HCl + NaOH  NaCl + H 2 O Using (MacidVacid = MbaseVbase), calculate the volume of 1.0 M HCl required to titrate 20.0 ml of 0.5 M, 1.0 M, and 2.0 M NaOH to the equivalence point. Show the calculations and record the HCl volumes in Table 1.

Chapter 14 Table of Contents B. Buffered Solutions Buffered solution – resists a change in its pH when either an acid or a base has been added –Presence of a weak acid and its conjugate base buffers the solution

Chapter 14 Table of Contents B. Buffered Solutions

Chapter 14 Table of Contents 1.To learn about acid-base titrations 2.To demonstrate calculations and techniques for titration lab 3.To understand the general characteristics of buffered solutions 4.Work Session: Next slide… Objectives Review

Chapter 14 Table of Contents C. Lab Techniques Buret Filling Buret Clearing Buret Reading Carol

Chapter 14 Table of Contents 1.What is true about [H+] and [OH-] at the equivalence point? 2.List two ways to determine the equivalence point. 3.Determine the volume of M NaOH needed to titrate ml of M HCl. Work Session

Chapter 14 Table of Contents 1.This is the end of the required material for this chapter… Objectives Review

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

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