2. POINT > Review acid-base neutralization POINT > Identify pH indicators and how they work POINT > Describe titration process

3. POINT > Review acid-base neutralization Recall that acids and bases can react with each other to form water and salt HCl + NaOH  H 2 O + Na + + Cl - This is an acid-base neutralization reaction

4. POINT > Review acid-base neutralization Recall that acids and bases can react with each other to form water and salt HCl + NaOH  H 2 O + Na + + Cl - The stoichiometry of this reaction shows that one mole of HCl neutralizes one mole of NaOH

5. POINT > Review acid-base neutralization Recall that acids and bases can react with each other to form water and salt 2HCl + Ba(OH) 2  2H 2 O + Ba 2+ + 2Cl - The stoichiometry of this reaction shows that two moles of HCl neutralize one mole of Ba(OH) 2

6. WB CHECK How many moles of calcium hydroxide are required to neutralize 3 moles of nitric acid? 3 mol HNO 3 x 1 mol Ca(OH) 2 = 1.5mol Ca(OH) 2 2mol HNO 3 2HNO 3 + Ca(OH) 2  2H 2 O + Ca 2+ + 2NO 3 -

7. POINT > Review acid-base neutralization We can use stoichiometry to calculate moles of an unknown acid or base, if we have a known acid or base solution to neutralize with 2HCl + Ba(OH) 2  2H 2 O + Ba 2+ + 2Cl -

8. POINT > Review acid-base neutralization Suppose 40.0 ml of 0.200M HCl neutralizes 100.0 ml of a Ba(OH) 2 solution. What is the concentration of the Ba(OH) 2 solution? 0.040 L HCl x 0.200mol/L = 0.0080 mol HCl 0.0080 mol HCl x = 0.0040 mol Ba(OH) 2 0.0040 mol Ba(OH) 2 / 0.100L = 0.040 M Ba(OH) 2 2HCl + Ba(OH) 2  2H 2 O + Ba 2+ + 2Cl - 1 mol Ba(OH) 2 2 mol HCl

9. POINT > Identify pH indicators and how they work How do we know when neutralization has occurred? pH indicators are compounds that change color at specific pH values pH indicators (HIn) are weak acids (or bases): HIn ↔ H + + In -

10. POINT > Identify pH indicators and how they work HIn ↔ H + + In - Depending on pH, one side of the equation will be favored HIn and In - have very different colors Different indicators have different transition intervals (the pH range where the color changes)

11. POINT > Identify pH indicators and how they work

12. POINT > Describe the titration process Titration is used to determine the concentration of a solution. A known volume of that solution is reacted with a solution of known concentration A measured volume of the acid or base of unknown concentration is placed in a flask. The neutralizing acid or base is added until a pH indicator changes color

13. POINT > Describe the titration process The known, standard solution is filled in a burette A few drops of acid-base indicator are added to the flask The standard solution is slowly added to the unknown solution in the flask As the two solutions are mixed the acid and the base are neutralized and the color changes

14. POINT > Describe the titration process Standard solution or titrant– A solution whose concentration is known End point: The point at which an indicator changes color Equivalence point: The point at which moles of H + from the acid equals moles of OH – from the base. An abrupt change in pH occurs at the equivalence point

15. The pH of the solution changes slowly until it nears equivalence It then changes rapidly 1 or 2 added drops will drastically change the indicator color POINT > Describe the titration process

16. The pH of the solution changes slowly until it nears equivalence POINT > Describe the titration process

17. WB CHECK: What is a “standard solution”? What is an endpoint? How does a pH indicator tell you neutralization has occurred?

18. WB CHECK: 43.0 mL of sodium hydroxide is titrated against 32.0 mL of 0.100 M hydrochloric acid. What is the molarity of the sodium hydroxide solution? [NaOH] = 0.0744 M

19. Homework: Read Chapter 15.2 pages 483-493 Practice #1-2 page 493 F.A. page 493 Titration Practice Worksheet