Chapter 15 Preview Lesson Starter Objectives Hydronium Ions

Chapter 15 Preview • • • Lesson Starter Objectives Hydronium Ions and Hydroxide Ions The p. H Scale Calculations Involving p. H

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Lesson Starter • Describe what is taking place during the selfionization of water.

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Objectives • Describe the self-ionization of water. • Define p. H, and give the p. H of a neutral solution at 25°C. • Explain and use the p. H scale. • Given [H 3 O+] or [OH−], find p. H. • Given p. H, find [H 3 O+] or [OH−].

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions Self-Ionization of Water • In the self-ionization of water, two water molecules produce a hydronium ion and a hydroxide ion by transfer of a proton. • In water at 25°C, [H 3 O+] = 1. 0 × 10− 7 M and [OH−] = 1. 0 × 10− 7 M. • The ionization constant of water, Kw, is expressed by the following equation. Kw = [H 3 O+][OH−]

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Self-Ionization of Water, continued • At 25°C, Kw = [H 3 O+][OH−] = (1. 0 × 10− 7) = 1. 0 × 10− 14 • Kw increases as temperature increases

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Neutral, Acidic, and Basic Solutions • Solutions in which [H 3 O+] = [OH−] is neutral. • Solutions in which the [H 3 O+] > [OH−] are acidic. • [H 3 O+] > 1. 0 × 10− 7 M • Solutions in which the [OH−] > [H 3 O+] are basic. • [OH−] > 1. 0 × 10− 7 M

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–] • Strong acids and bases are considered completely ionized or dissociated in weak aqueous solutions. 1 mol • 1. 0 × 10− 2 M Na. OH solution has an [OH−] of 1. 0 × 10− 2 M • The [H 3 O+] of this solution is calculated using Kw. Kw = [H 3 O+][OH−] = 1. 0 × 10− 14

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–] • If the [H 3 O+] of a solution is known, the [OH−] can be calculated using Kw. [HCl] = 2. 0 × 10− 4 M [H 3 O+] = 2. 0 × 10− 4 M Kw = [H 3 O+][OH−] = 1. 0 × 10− 14

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Some Strong Acids and Some Weak Acids

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Concentrations and Kw

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–] Sample Problem A A 1. 0 10– 4 M solution of HNO 3 has been prepared for a laboratory experiment. a. Calculate the [H 3 O+] of this solution. b. Calculate the [OH–].

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–], continued Sample Problem A Solution Given: Concentration of the solution = 1. 0 × 10− 4 M HNO 3 Unknown: a. [H 3 O+] b. [OH−] Solution: • HNO a. 3 is a strong acid 1 mol

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–], continued Sample Problem A Solution, continued a. b. [H 3 O+][OH−] = 1. 0 × 10− 14

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Hydronium Ions and Hydroxide Ions, continued Calculating [H 3 O+] and [OH–], continued Sample Problem A Solution, continued a. b.

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H 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+] • example: a neutral solution has a [H 3 O+] = 1× 10− 7 • The logarithm of 1× 10− 7 is − 7. 0. p. H = −log [H 3 O+] = −log(1 × 10− 7) = −(− 7. 0) = 7. 0

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Values as Specified [H 3 O+]

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H The p. H Scale • 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–] • example: a neutral solution has a [OH–] = 1× 10− 7 • The p. H = 7. 0. • The negative logarithm of Kw at 25°C is 14. 0. p. H + p. OH = 14. 0

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H p. OH Click below to watch the Visual Concept

Chapter 15 The p. H Scale Section 1 Aqueous Solutions and the Concept of p. H

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Approximate p. H Range of Common Materials

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H [H 3 O+], [OH–], p. H and p. OH of Solutions

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Comparing p. H and p. OH Click below to watch the Visual Concept

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H • There must be as many significant figures to the right of the decimal as there are in the number whose logarithm was found. • example: [H 3 O+] = 1 × 10− 7 one significant figure p. H = 7. 0

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Using Logarithms in p. H Calculations

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued Calculating p. H from [H 3 O+], continued Sample Problem B What is the p. H of a 1. 0 10– 3 M Na. OH solution?

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued Calculating p. H from [H 3 O+], continued Sample Problem B Solution Given: Identity and concentration of solution = 1. 0 × 10− 3 M Na. OH Unknown: p. H of solution Solution: concentration of base → concentration of OH− → concentration of H 3 O+ → p. H [H 3 O+][OH−] = 1. 0 × 10− 14 p. H = −log [H 3 O+] = −log(1. 0 × 10− 11) = 11. 00

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued Calculating p. H from [H 3 O+], continued • p. H = −log [H 3 O+] • log [H 3 O+] = −p. H • [H 3 O+] = antilog (−p. H) • [H 3 O+] = 10−p. H • The simplest cases are those in which p. H values are integers.

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued Calculating [H 3 O+] and [OH–] from p. H, continued Sample Problem D Determine the hydronium ion concentration of an aqueous solution that has a p. H of 4. 0.

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued Calculating [H 3 O+] and [OH–] from p. H, continued Sample Problem D Solution Given: p. H = 4. 0 Unknown: [H 3 O+] Solution: [H 3 O+] = 10−p. H [H 3 O+] = 1 × 10− 4 M

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Calculations Involving p. H, continued p. H Calculations and the Strength of Acids and Bases • The p. H of solutions of weak acids and weak bases must be measured experimentally. • The [H 3 O+] and [OH−] can then be calculated from the measured p. H values.

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H of Strong and Weak Acids and Bases

Chapter 15 Section 1 Aqueous Solutions and the Concept of p. H Values of Some Common Materials

Chapter 15 Section 2 Determining p. H and Titrations Preview • • Objectives Indicators and p. H Meters Titration Molarity and Titration

Chapter 15 Section 2 Determining p. H and Titrations Objectives • Describe how an acid-base indicator functions. • Explain how to carry out an acid-base titration. • Calculate the molarity of a solution from titration data.

Chapter 15 Section 2 Determining p. H and Titrations Indicators and p. H Meters • Acid-base indicators are compounds whose colors are sensitive to p. H. • Indicators change colors because they are either weak acids or weak bases. • HIn and In− are different colors. • In acidic solutions, most of the indicator is HIn • In basic solutions, most of the indicator is In–

Chapter 15 Section 2 Determining p. H and Titrations Indicators and p. H Meters • The p. H range over which an indicator changes color is called its transition interval. • Indicators that change color at p. H lower than 7 are stronger acids than the other types of indicators. • They tend to ionize more than the others. • Indicators that undergo transition in the higher p. H range are weaker acids.

Chapter 15 Section 2 Determining p. H and Titrations Indicators and p. H Meters • A p. H meter determines the p. H of a solution by measuring the voltage between the two electrodes that are placed in the solution. • The voltage changes as the hydronium ion concentration in the solution changes. • Measures p. H more precisely than indicators

Chapter 15 Section 2 Determining p. H and Titrations Color Ranges of Indicators

Chapter 15 Section 2 Determining p. H and Titrations Color Ranges of Indicators

Chapter 15 Section 2 Determining p. H and Titrations Color Ranges of Indicators

Chapter 15 Section 2 Determining p. H and Titrations Titration • Neutralization occurs when hydronium ions and hydroxide ions are supplied in equal numbers by reactants. H 3 O+(aq) + OH−(aq) 2 H 2 O(l) • Titration is the controlled addition and measurement of the amount of a solution of known concentration required to react completely with a measured amount of a solution of unknown concentration.

Chapter 15 Section 2 Determining p. H and Titrations Titration, continued Equivalence Point • The point at which the two solutions used in a titration are present in chemically equivalent amounts is the equivalence point. • The point in a titration at which an indicator changes color is called the end point of the indicator.

Chapter 15 Section 2 Determining p. H and Titrations Titration, continued Equivalence Point, continued • Indicators that undergo transition at about p. H 7 are used to determine the equivalence point of strongacid/strong base titrations. • The neutralization of strong acids with strong bases produces a salt solution with a p. H of 7.

Chapter 15 Section 2 Determining p. H and Titrations Titration, continued Equivalence Point, continued • Indicators that change color at p. H lower than 7 are used to determine the equivalence point of strongacid/weak-base titrations. • The equivalence point of a strong-acid/weak-base titration is acidic.

Chapter 15 Section 2 Determining p. H and Titrations Titration, continued Equivalence Point, continued • Indicators that change color at p. H higher than 7 are used to determine the equivalence point of weakacid/strong-base titrations. • The equivalence point of a weak-acid/strong-base titration is basic.

Chapter 15 Titration Curve for a Strong Acid and a Strong Base Section 2 Determining p. H and Titrations

Chapter 15 Titration Curve for a Weak Acid and a Strong Base Section 2 Determining p. H and Titrations

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration • The solution that contains the precisely known concentration of a solute is known as a standard solution. • A primary standard is a highly purified solid compound used to check the concentration of the known solution in a titration • The standard solution can be used to determine the molarity of another solution by titration.

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 1

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 1

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 1

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 2

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 2

Chapter 15 Section 2 Determining p. H and Titrations Performing a Titration, Part 2

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued • To determine the molarity of an acidic solution, 10 m. L HCl, by titration 1. Titrate acid with a standard base solution 20. 00 m. L of 5. 0 × 10− 3 M Na. OH was titrated 2. Write the balanced neutralization reaction equation. HCl(aq) + Na. OH(aq) Na. Cl(aq) + H 2 O(l) 1 mol 3. Determine the chemically equivalent amounts of HCl and Na. OH.

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued 4. Calculate the number of moles of Na. OH used in the titration. • 20. 0 m. L of 5. 0 × 10− 3 M Na. OH is needed to reach the end point 5. amount of HCl = mol Na. OH = 1. 0 × 10− 4 mol 6. Calculate the molarity of the HCl solution

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued 1. Start with the balanced equation for the neutralization reaction, and determine the chemically equivalent amounts of the acid and base. 2. Determine the moles of acid (or base) from the known solution used during the titration. 3. Determine the moles of solute of the unknown solution used during the titration. 4. Determine the molarity of the unknown solution.

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F In a titration, 27. 4 m. L of 0. 0154 M Ba(OH)2 is added to a 20. 0 m. L sample of HCl solution of unknown concentration until the equivalence point is reached. What is the molarity of the acid solution?

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F Solution Given: volume and concentration of known solution = 27. 4 m. L of 0. 0154 M Ba(OH)2 Unknown: molarity of acid solution Solution: 1. balanced neutralization equation chemically equivalent amounts Ba(OH)2 + 2 HCl 1 mol 2 mol Ba. Cl 2 + 2 H 2 O 1 mol 2 mol

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F Solution, continued 2. volume of known basic solution used (m. L) amount of base used (mol) 3. mole ratio, moles of base used moles of acid used from unknown solution

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F Solution, continued 4. volume of unknown, moles of solute in unknown molarity of unknown

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F Solution, continued 1. 1 mol Ba(OH)2 for every 2 mol HCl. 2. 3.

Chapter 15 Section 2 Determining p. H and Titrations Molarity and Titration, continued Sample Problem F Solution, continued 4.

End of Chapter 15 Show