2. Friday, May 6th: “A” Day Agenda
Homework questions/problems/collect
Quiz over section 15.2: “Acidity, Basicity, and pH”
Section 15.3: “Neutralizations and Titrations”
Neutralization reaction, equivalence point, titration, titrant, standard solution, transition range, end point
Homework:
Sec review, pg. 556: #1-10
Concept Review: “Neutralizations and Titrations”
Lab Write-Up: “Titration of an Acid and a Base”

3. Section 15.2 Quiz “Acidity, Basicity, and pH”
You may use your guided notes, your book, and a partner to complete the quiz.

4. H3O+(aq) + OH−(aq)  2 H2O(l)
Neutralization
Neutralization reaction: the reaction of hydronium ions and hydroxide ions to form water molecules and a salt.
When solutions of a strong acid and a strong base, having exactly equal amounts of H3O+(aq) and OH−(aq) ions, are mixed, almost all of the hydronium and hydroxide ions react to form water.
H3O+(aq) + OH−(aq)  2 H2O(l)
*correct*

5. Neutralization
Suppose that hydrochloric acid, HCl, and sodium hydroxide, NaOH are mixed.
The result will be a solution of only water and the spectator ions sodium and chlorine.
This is just a solution of sodium chloride.
HCl + NaOH  NaCl + H2O
This representation can be misleading because the only reactants are H3O+(aq) and OH−(aq) ions and the only product is H2O.

6. Titrations
If an acidic solution is added gradually to a basic solution, at some point the neutralization reaction ends because the hydroxide ions are used up.
Likewise, if a basic solution is added to an acid, eventually all of the hydronium ions will be used up.
The point at which a neutralization reaction is complete is known as the equivalence point.
Equivalence point: the point at which the two solutions used in a titration are present in chemically equivalent amounts.

7. Titrations
When a solution of a strong base is added to a solution of a strong acid, the equivalence point occurs when the amount of added hydroxide ions equals the amount of hydronium ions originally present.
Titration: the gradual addition of one solution to another to reach an equivalence point.
The purpose of a titration is to determine the concentration of an acid or a base.

8. Titration
In addition to the two solutions, the equipment needed to carry out a titration usually includes two burets, a titration flask, and a suitable indicator.
One buret is for the acid solution, the other is for the basic (alkaline) solution.
Titrant: a solution of known concentration that is used to titrate a solution of unknown concentration.

9. Titration
To find the concentration of the solution being titrated, you must already know the concentration of the titrant.
Standard solution: a solution of known concentration.
The concentration of a standard solution has usually been determined by reacting the solution with a precisely weighed mass of a solid acid or base.

10. Titration
A distinctively shaped graph, called a titration curve, results when pH is plotted against titrant volume.
Because the curve is steep at the equivalence point, it is easy to locate the exact volume that corresponds to a pH of 7.00.
A titration is exact only if the equivalence point can be accurately detected.

11. Equivalence Point
This graph of pH versus the volume of M NaOH added to an HCl solution indicates that the equivalence point occurred after 38.6 mL of titrant was added.

12. Indicators
Transition range: the pH range through which an indicator changes color.
End point: the point in a titration at which a marked color change takes place.
If an appropriate indicator is chosen, the end point and the equivalence point will be the same.

13. Selecting an Indicator
In titrations of a strong acid by a strong base, the equivalence point occurs at pH 7.
When a weak acid is titrated by a strong base, the equivalence point is at a pH greater than 7.
The titration of a weak base and a strong acid, the equivalence point is at a pH less than 7.

14. How to Perform a Titration

15. How to Perform a Titration

16. Titration Calculations
At the equivalence point in a titration of a strong acid by a strong base, the amount of hydroxide ion added equals the initial amount of hydronium ion.
C: concentration (in moles per liter)
V: volume (in liters) of the solution

17. Titration Calculations
An easier way to think of this:
(C Acid)(V Acid) = (C Base) (V Base)
C: concentration (in moles per liter)
V: volume (in liters) of the solution

18. (CAcid) (VAcid) = (CBase) (VBase)
Sample Problem D, pg. 555 Calculating Concentration from Titration Data
A student titrates mL of an HCl solution of unknown concentration with a M NaOH solution. The volume of base solution needed to reach the equivalence point is mL. What is the concentration of the HCl solution in moles/liter?
(CAcid) (VAcid) = (CBase) (VBase)

19. Sample Problem D, continued…
NaOH is a strong base so:
NaOH Na + + OH-
M M
C(acid) = ?
V(acid) = mL = .04L
C(base) = M
V(base) = mL = L
(CAcid) (VAcid) = (CBase) (VBase)
C (Acid) (.04 L) =( M) ( L)
C(acid) = mol/L

20. Additional Practice
If 72.1 mL of M H2SO4 completely titrates 39.0 mL of KOH solution, what is the molarity of the KOH solution?
H2SO4 is a strong acid so:
H2SO H2O SO H3O +
0.543 M M
Because of the 1:2 ratio, 1 mole of H2SO4 makes 2 moles of H3O +.
[H3O+] = 2 [H2SO4] = 2 (0.543 M) = M

21. Additional Practice, continued…
(CAcid) (VAcid) = (CBase) (VBase)
C(acid) = M
V(acid) = 72.1 mL = L
C(base) = ?
V(base) = 39.0 mL = L
(1.086 M) (.0721 L) = (C Base) (.0390L)
C(base) = 2.01 M

22. U of I 3D-Printing Presentation on Tuesday! Titration lab on Thursday
Homework
Section 15.3 review, pg. 556: #1-10
Concept Review: “Neutralizations and Titrations”
Lab Write-Up: “Titration of an Acid and a Base”
Looking Ahead:
U of I 3D-Printing Presentation on Tuesday!
Titration lab on Thursday
No Flip-Flops!