Unit 2: Acid-Base & Non-Aqueous Titrations

Semester 1

BP102T

Introduction to Acid-Base & Non-Aqueous Titrations

Unit 2 dives into the most common type of analysis: Acid-Base Titrations. You will understand how indicators work and how to select the right one based on titration curves. The second half covers Non-Aqueous Titrations, a crucial technique for analyzing drugs that don’t dissolve or react well in water, using solvents like Glacial Acetic Acid.

Syllabus & Topics

1Acid-Base Titration: Theories of acid-base indicators (Ostwald’s, Quinonoid)
2Classification of Acid-Base Titrations (SA-SB, WA-SB, SA-WB, WA-WB)
3Neutralization Curves for different titrations
4Non-Aqueous Titration: Solvents (Protophilic, Protogenic, Amphiprotic, Aprotic)
5Acidimetry and Alkalimetry in non-aqueous media
6Estimation of Sodium Benzoate
7Estimation of Ephedrine HCl

Learning Objectives

Explain the theories of Acid-Base indicators.

Draw and interpret Neutralization Curves.

Classify solvents used in Non-Aqueous Titration.

Describe the procedure for Estimating Sodium Benzoate.

Understand the principle of assay of Ephedrine HCl.

Frequently Asked Questions (FAQs)

Q1. Why do we use non-aqueous titrations?

Non-aqueous titrations are used for substances that are too weak to be titrated in water (very weak acids or bases) or are insoluble in water. Solvents such as glacial acetic acid enhance the acidic or basic strength of the analyte, making accurate titration possible.

Q2. What is the role of Perchloric acid in non-aqueous titration?

Perchloric acid (HClO₄) acts as a very strong acid in non-aqueous solvents like glacial acetic acid and is commonly used as a titrant for weak bases.

Q3. What is the Leveling Effect?

The leveling effect occurs when a solvent makes all strong acids appear to have the same strength. For example, in water, HCl and H₂SO₄ both behave as equally strong acids. To distinguish between them, a differentiating solvent is required.

Q4. How is Sodium Benzoate estimated?

Sodium benzoate is a weak base salt. It is titrated against standard perchloric acid in a non-aqueous medium (usually glacial acetic acid) using crystal violet as an indicator.

Q5. What are Neutralization Curves?

Neutralization curves are plots of pH versus volume of titrant added. They help in selecting the appropriate indicator for a titration. The shape of the curve depends on the strength of the acid and base, such as strong acid–strong base or weak acid–strong base systems.