(SEM III) THEORY EXAMINATION 2022-23 PHYSICAL PHARMACEUTICS I

SECTION A – Short Answer Section

This section contains short conceptual questions related to solubility, surfactants, buffers, complexation, and surface chemistry used in pharmaceutical formulations.

Question 1: Define Eutectic Mixture with Example.

Answer:
A eutectic mixture is a mixture of two or more components that melts at a lower temperature than either of the individual components.

Example:
Mixture of menthol and camphor forms a eutectic mixture.

Question 2: Define Buffer Capacity.

Answer:
Buffer capacity is the ability of a buffer solution to resist changes in pH when small amounts of acid or base are added.

Higher buffer capacity means the solution can maintain its pH more effectively.

Question 3: Define Sorensen’s pH Scale.

Answer:
Sorensen’s pH scale is a measure of acidity or alkalinity of a solution.

Formula:

pH=−log⁡[H+]pH = -\log [H^+]pH=−log[H+]

The pH scale ranges from 0 to 14.

SECTION B – Long Answer Section

This section requires detailed explanations of surface tension, complex formation, and solubility behavior of liquids in pharmaceutical systems.

Question 1: Methods for Determination of Surface and Interfacial Tension.

Answer:

Surface tension can be determined using several methods:

Capillary Rise Method
Measures the height of liquid rise in a capillary tube.

Drop Weight Method
Measures weight of drops formed from liquid.

Du Noüy Ring Method
Uses a platinum ring to measure the force required to detach a liquid film.

These methods are important in studying emulsions and drug absorption.

Question 2: Classification of Complexation.

Answer:

Complexation occurs when two or more molecules combine to form a complex.

Types:

Metal Ion Complexes
Example: Chelates formed with EDTA.

Organic Molecular Complexes
Example: Charge transfer complexes.

Inclusion Complexes
Example: Cyclodextrin complexes.

Applications:

Improve drug solubility

Increase stability of drugs.

Question 3: Solubility of Liquids in Liquids.

Answer:

Liquids may be classified based on their miscibility:

Completely miscible liquids
Example: Alcohol + Water.

Partially miscible liquids
Example: Phenol + Water.

Immiscible liquids
Example: Oil + Water.

Factors affecting solubility:

Temperature

Nature of solute and solvent.

SECTION C – Descriptive Section

This section tests deeper knowledge of pharmaceutical physical chemistry concepts such as distribution law, buffers, optical activity, and physical states of solids.

Question 1: Explain Polarimeter and its Working.

Answer:

A polarimeter is an instrument used to measure the optical rotation of optically active substances.

Working Principle:
When polarized light passes through an optically active substance, the plane of polarized light rotates.

The angle of rotation depends on:

Concentration of substance

Length of sample tube

Nature of substance.

Applications:

Determination of sugar concentration

Identification of optically active drugs.

Question 2: Difference between Crystalline and Amorphous States.

Example:
Crystalline – Sodium chloride
Amorphous – Glass.

Question 3: Applications of Buffers in Pharmaceutical Systems.

Answer:

Buffers are widely used in pharmaceutical and biological systems.

Applications:

Maintain pH of injections and ophthalmic solutions

Improve drug stability

Maintain physiological pH in biological fluids

Used in analytical chemistry and drug formulation.