1. Titration

2. Titration Strong acids ionize almost completely
Weak acids don’t ionize very much
[H3O+1] not same as acid concentration

3. [H3O+1]
Can’t be measured directly
Determined by comparison

4. Acid-Base Titration Carefully controlled neutralization reaction
Requires standard solution &
acid-base indicator
Standard solution is: acid/base of
known concentration

5. Titration Standard solution slowly added to unknown solution
As solutions mix:
neutralization reaction occurs
Eventually:
enough standard solution is added to neutralize the unknown solution  Equivalence point

6. Equivalence point
Total # moles H+1 ions donated by acid = total # moles H+1 accepted by base
Total moles H+1 = total moles OH-1

7. Titration End-point = point at which indicator changes color
if indicator chosen correctly:
end-point very close to equivalence point

8. Titration of a strong acid with a strong base
14-
Phenolphthalein
Color change:
8.2 to  pH 7-
Equivalence Pt  0-   
Volume of M NaOH added (ml)
0 ml
40ml
20 ml

9. MH+1VH+1 = MOH-1VOH-1 MH+1 = molarity of H+1 MOH-1 = molarity of OH-1
VH+1 = volume of H+1
VOH-1 = volume of OH-1

10. MaVa = MbVb True for: monoprotic acids and monohydroxy bases
diprotic acids and dihydroxy bases
triprotic acids and trihydroxy bases

11. If:
# H’s in acid ≠ # OH’s in base need to modify equation:
(#H’s)(Ma)(Va) = (Mb)(Vb)(#OH’s)

12. Titration Problem #1
In a titration of 40.0 mL of a nitric acid solution, the end point is reached when 35.0mL of 0.100M NaOH is added
Calculate the concentration of the nitric acid solution

13. Neutralization Reaction
HNO3 + NaOH  H2O + NaNO3
HNO3 is a monoprotic acid
NaOH is a monohydroxy base

14. Variables
Ma = ?
Va = 40.0 mL
Mb = M
Vb = 35.0 mL

15. Plug and Chug
X (40.0 mL) = (0.100 M )(35.0 mL)
X = M HNO3

16. Titration Problem #2
What is the concentration of a hydrochloric acid solution if 50.0 mL of a 0.250M KOH solution are needed to neutralize 20.0mL of the HCl solution of unknown concentration?

17. Neutralization Reaction
KOH + HCl  H2O + KCl
HNO3 is a monoprotic acid
KOH is a monohydroxy base

18. Variables
Ma = X
Va = 20.0 mL
Mb = M
Vb = 50.0 mL

19. Plug and Chug
X (20.0 mL) = (0.250 M) (50.0 mL)
X = M HCl

20. Titration Problem #3
What is the concentration of a sulfuric acid solution if 50.0mL of a 0.25 M KOH solution are needed to neutralize 20.0mL of the H2SO4 solution of unknown concentration?

21. Neutralization Reaction
H2SO4 + 2 KOH  2 H2O + K2SO4
H2SO4 is a diprotic acid
KOH is a monohydroxy base

22. Variables
Ma = X
Va = 20.0mL
Mb = 0.25M
Vb = 50.0mL

23. Plug and Chug (2)(X)(20.0ml) = (0.25M)(50.0ml)(1)
X = M (sulfuric acid)