Introduction Alkalimetry and acidimetry Acid- base indicator References

1. ACID-BASE TITRATIONS
Prepared by
G. Nikitha, M.Pharmacy
Assistant Professor
Department of Pharmaceutical Chemistry
Sree Dattha Institute of Pharmacy
Hyderabad
Subject: Pharmaceutical Inorganic Chemistry
Year: Pharm-D 1st Year

2. CONTENT
 Introduction
 Alkalimetry and acidimetry
 Acid- base indicator
 References

3. LEARNING OBJECTIVES
In These topic we will discuss
 What is acid base titration, Alkalimetry and acidimetry, Acid- base indicator
 What are indicators are used in acid base titration

4. INTRODUCTION
An acid-base titration is a procedure used in quantitative chemical analysis to
determine the concentration of either acid or base by exactly neutralizing it with
a standard solution of base or acid having known concentration. An indicator is
used to monitor the progress of the acid–base reaction.

5. ALKALIMETRY AND ACIDIMETRY
 Alkalimetry and acidimetry are a kind of volumetric analysis in which the
fundamental reaction is a neutralization reaction.
 Acidimetry is the specialized analytic use of acid-base titration to determine the
concentration of a basic (synonymous to alkaline) substances using standard
acid. In acidimetry, a known volume of a base is put into a conical flask. This
solution is then titrated against a standard solution of acid taken in a burette till
an equivalent quantity of acid is added to base. The point at which the acid and
base are added in equivalent amount is termed as the equivalent point. If both
the acid base are strong electrolytes resulting solution would be neutral and is
pH 7. On the other hand if acid or base or both acid and base are weak
electrolytes, the salt formed gets hydrolyzed to a certain extent and the resulting
solution would be slightly acidic or basic at the equivalence point and pH will
not be seven.

6.  Alkalimetry used to determine the concentration of a acid substances using
standard base . In alkalimetry a known volume of an acid is put into a conical
flask. This solution is then titrated against a standard solution of base taken in a
burette till an equivalent quantity of base is added to the acid. The point at
which the acid and base are added in equivalent amount is termed as the
equivalent point. If both the acid base are strong electrolytes resulting solution
would be neutral and is pH 7. On the other hand if acid or base or both acid and
base are weak electrolytes, the salt formed gets hydrolyzed to a certain extent
and the resulting solution would be slightly acidic or basic at the equivalence
point and pH will not be seven.

7. ACID- BASE INDICATOR
 These are the indicators which are used in acid-base titrations to locate
their equivalence point. These indicators have one colour in acid
solution while an altogether different colour in basic solution.
 The colour change of an acid-base indicator is not sudden but takes
place within a small range of pH value. This range is called the pH range
of an indicator.

8. The pH ranges of various acid-base indicators are given below
Colour range of various acid-base indicators
Indicator pH range Colour in acid Colour in base
Phenolphthalein 8.3-10.5 Colourless Red
Litmus 5.5-7.4 Red Red
Methyl red 4.5-6.5 Red Yellow
Methyl Orange 3.2-4.5 Pink Yellow

9. Choice of indicator in various acid-base titrations
Titrant
Electrolyte
(Acid)
Titrant
Electrolyte
(base)
Indicator Colour change
Strong
HCl, H2SO4
Strong
NaOH, KOH
Methyl Orange or
Phenolphthalein
Red to yellow
Colourless to pink
Strong
H2SO4
weak
NH4OH
Methyl Orange or
Methyl red
Red to yellow
Red to yellow
Weak
CH3COOH
Strong
NaOH
Phenolphthalein Colourless to pink
Weak
CH3COOH
Weak
NH4OH
None is suitable

10. CONCLUSION
In These topic we have discussed that
 What is acid base titration, Alkalimetry and acidimetry, Acid- base indicator
 What are indicators are used in acid base titration

11. REFERENCE
 Pharmaceutical Chemistry -Inorganic Volume-1 by G. R. Chatwal.
 Essentials of Inorganic Chemistry by Katja A. Strohfeldt.
 Indian Pharmacopoeia.
 M.L Schroff, Inorganic Pharmaceutical Chemistry.
 P. GunduRao, Inorganic Pharmaceutical Chemistry, 3rd Edition
 A.I. Vogel, Text Book of Quantitative Inorganic analysis.
 Bentley and Driver's Textbook of Pharmaceutical Chemistry.

12. THANK YOU