1. WEEK 6
PROCEDURE OF TITRATIONS
ACID-BASE TITRATIONS

2. What is acid-base titration?
A TITRATION WHICH DEALS WITH A
REACTION INVOLVING ACID AND A
BASE.
What is a titration?
The act of adding standard solution in small quantities to the test solution till the reaction is complete is termed titration.

3. What is a standard solution?
A standard solution is one whose
concentration is precisely known.
What is a test solution?
A test solution is one whose
concentration is to be estimated

4. Titration of Vinegar against NaOH
Vinegar is an acetic acid solution of certain
concentration
So a titration of vinegar against NaOH actually
means, a reaction between acetic acid and NaOH.
HC2H3O2(aq) NaOH(aq)  NaC2H3O H2O(l)
Sodium
hydroxide
Sodium
Acetate
Acetic acid
water
water
Acid
Base
salt

5. Titration of Vinegar against NaOH
HC2H3O2(aq) NaOH(aq)  NaC2H3O H2O(l)
CH3COOH(aq) NaOH(aq)  CH3COONa + H2O(l)
1 molecule
1 molecule
1 molecule
1 molecule
1 mole
1 mole
1 mole
1 mole
1 mole CH3COOH ≡ 1 mole NaOH

6. Titration of Vinegar against NaOH
In this experiment, we are trying to find the
[CH3COOH] in vinegar. So we have to know the
[NaOH] accurately first, before finding the
[CH3COOH] in Vinegar.
Finding the [NaOH] should be pretty easy right?!!

7. How hard is it to make 500 mL of 0.1 M NaOH?
Should not be that hard right?!!
Calculate the weight of NaOH (2.0 g)
Weigh out the NaOH on the balance
Dissolve it in 500 mL of water in a volumetric flask
Hold on! We have a problem here!!

8. So what is your problem? What do you mean by hygroscopic?
I don’t have a problem but Mr. NaOH
seems to have a problem here
NaOH is hygroscopic..
What do you mean by hygroscopic?
It absorbs moisture. NaOH absorbs moisture from air.

9. What if NaOH is hygroscopic?
Let us say, for the problem at hand,
we need 2.0 g NaOH to make a 0.1 M
NaOH solution. By the time we weigh
out the NaOH for our solution, it
would have absorbed moisture. So the
total weight of 2.0 g is not all due to
NaOH. It has some contribution from
the water that the NaOH absorbed.

10. How do we find the [NaOH] precisely? What is standardization?
Through standardization
What is standardization?
It is just a technical term for doing
a titration using a primary standard
to find the precise concentration of a secondary standard.

11. What is a primary standard?
A primary standard should possess the following qualities:
(i) It must be available in very pure form
(ii) It should not be affected by exposure to moisture or air.
(iii) It should maintain its purity during storage.
(iv) The reactions involving the primary standard should
be stoichiometric and fast.
(v) It should have high molecular weight.

12. Which primary standard are we
going to use?
Potassium hydrogen phthalate, abbreviated as KHP.
Remember!! KHP is not the molecular formula for
Potassium hyrogen phthalate. It is just an abbreviation.
So when calculating the molecular weight of KHP,
do not add up the atomic weights of K, H and P.
COOH
C-H
COOK CH HC
Potassium Hydrogen Phthalate, KHC8H4O4

13. Standardization KHC8H4O4(aq) + NaOH(aq)  KNaC8H4O4 + H2O(l) water
Acid
Base
salt
1 molecule
1 molecule
1 molecule
1 molecule
1 mole
1 mole
1 mole
1 mole
1 mole KHC8H4O4 ≡ 1 mole NaOH

14. Standardization Vfinal- Vinital= Vused (in mL) Vinitial
moles of KHP = Moles of NaOH
moles of KHP
= MNaOH × VNaOH
“ 0.1 M
NaOH ”
Vfinal
moles of KHP
= MNaOH × Vused
End point:
Pale Permanent
Pink color
250mL
250mL
250mL
KHP + H2O+ 2-3 drops of phenolphthalein

15. Titration of Vinegar vs. NaOH
Vfinal- Vinital= Vused (in mL)
Vinitial
moles of acetic acid
= Moles of NaOH
moles of acetic acid
= MNaOH × VNaOH
“ 0.1 M
NaOH ”
Vfinal
moles of acetic acid
= MNaOH × Vused
End point:
Pale Permanent
Pink color
250mL
250mL
250mL
vinegar + H2O+ 2-3 drops of phenolphthalein

16. Titration Basics First Derivative Curve Shows where change is greatest
Titration = addition of a measurable volume of a known solution (titrant) to an unknown solution until it is just consumed
Use the stoichiometry of the reaction of the known and unknown to calculate the concentration of the unknown solution
A pH curve shows the change in pH versus volume of titrant as the titration proceeds
pH meter can be used to monitor
pH during the titration
2) An acid-base indicator can be used
to signal reaching the equivalence point
First Derivative Curve
Shows where change is greatest

17. 3) Important points:
pH increases slowly far from the equivalence point
pH changes quickly near the equivalence point
The equivalence point of a strong acid—strong base titration = 7.00

18. Titration Curves
 A titration curve is a graph of the pH changes that occur during an acid-base titration versus the volume of acid or base added.
There are three types of titration curves.
You need to be able to recognize each and then choose a suitable indicator for that titration.
The equivalence point is the end of a titration where the stoichiometry of the reaction is exactly satisfied, or moles H+ = moles OH-.
The transition point refers to when an indicator changes color and [HInd] = [Ind-].

19. Choosing an Indicator
When you choose an indicator, you must pick one so that the transition point of the indicator matches the equivalence point of the titration.
When acid base titration is at the equivalence point, the acid has neutralized the base leaving only a salt and water.
The pH of the equivalence point depends on type of salt.
Rule of thumb
If the salt is neutral the equivalence point = 7
If the salt is basic the equivalence point = 9
If the salt is acidic the equivalence point = 5

20. 1. Titration Curve: Strong Acid and Strong Base
HCl KOH →

21. 1. Titration Curve: Strong Acid and Strong Base
HCl KOH → KCl HOH

22. 1. Titration Curve: Strong Acid and Strong Base
HCl KOH → KCl HOH
Indicator

23. 1. Titration Curve: Strong Acid and Strong Base
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue

24. 1. Titration Curve: Strong Acid and Strong Base
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl

25. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7 25 50

26. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7
0.10 M HCl 25 50

27. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7
0.10 M HCl
Neutral Salt 25 50

28. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7
0.10 M KOH
0.10 M HCl
Neutral Salt 25 50

29. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7 25 50

30. 1. Titration Curve: Strong Acid and Strong Base HCl + KOH → KCl + HOH
HCl KOH → KCl HOH
Indicator pH = 7 Bromothymol Blue
50 mL of 0.10 M KOH is added to 25 mL of 0.10 M HCl pH
Volume .10 M KOH added 14 7 25 50

31. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH →

32. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH → KCN HOH

33. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH → KCN HOH
Indicator

34. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH → KCN HOH
Indicator pH = 9 Phenolphthalein

35. 2. Titration Curve: Weak Acid and Strong Base
HCN KOH → KCN HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH

36. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7 10 20

37. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7
1.0 M KOH 10 20

38. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7
1.0 M KOH
Basic Salt 10 20

39. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7
1.0 M KOH
Basic Salt
1.0 M HCN 10 20

40. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7
1.0 M KOH
Basic Salt
1.0 M HCN 10 20

41. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH pH
Volume 1.0 M HCN added 14 7 10 20

42. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
Buffer Zone pH
Volume 1.0 M HCN added 14 7 10 20

43. 2. Titration Curve: Weak Acid and Strong Base HCN + KOH → KCN + HOH
Indicator pH = 9 Phenolphthalein
20 mL of 1.0 M HCN is added to 10 mL of 1.0 M KOH
Buffer Zone
Weak Acid & Salt
are present pH
Volume 1.0 M HCN added 14 7 10 20

44. 3. Titration Curve: Strong Acid and Weak Base
HCl NH3 →

45. 3. Titration Curve: Strong Acid and Weak Base
HCl NH3 → NH4+ + Cl-

46. 3. Titration Curve: Strong Acid and Weak Base
HCl NH3 → NH4+ + Cl-
Indicator

47. 3. Titration Curve: Strong Acid and Weak Base
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red

48. 3. Titration Curve: Strong Acid and Weak Base
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl

49. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7 30 60

50. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7
1.0 M HCl 30 60

51. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7
1.0 M HCl
Acid Salt 30 60

52. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7
1.0 M NH3
1.0 M HCl
Acid Salt 30 60

53. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7 30 60
1.0 M NH3
1.0 M HCl
Acid Salt

54. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7 30 60

55. 3. Titration Curve: Strong Acid and Weak Base HCl + NH3 → NH4+ + Cl-
HCl NH3 → NH4+ + Cl-
Indicator pH = 5 Methyl Red
60 mL of 1.0 M NH3 is added to 30 mL of 1.0 M HCl pH
Volume 1.0 M NH3 added 14 7
Buffer Zone
Weak Base & Salt
are present 30 60

56. 4. Match the Curve with the ReactionpH
Volume .10 M KOH added 14 7 25 50
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

57. 4. Match the Curve with the ReactionpH
Volume .10 M KOH added 14 7 25 50
Bisect the verticle
pH = 7
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

58. 4. Match the Curve with the ReactionpH
Volume .10 M KOH added 14 7 25 50
Bisect the verticle
pH = 7
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

59. 5. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

60. 5. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7
Bisect the verticle
pH = 5 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

61. 6. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

62. 6. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7
Bisect the verticle
pH = 9 30 60
A. 3HCl Al(OH)2 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH

63. 6. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7
Bisect the verticle
pH = 9 30 60
A. 3HCl Al(OH)2 → AlCl HOH
B. HCl KOH → KCl HOH
C. HCN KOH → KCN HOH