SECTION A – Short Answer Section
This section contains short conceptual questions related to solution chemistry, buffers, surface phenomena, and pharmaceutical physical chemistry concepts. These questions test the basic understanding of fundamental terms used in drug formulation and pharmaceutical systems.
Question 1: Define Critical Solution Temperature (CST) with example.
Answer:
Critical Solution Temperature (CST) is the temperature at which two partially miscible liquids become completely miscible in all proportions.
Example:
Phenol and water system shows upper critical solution temperature (UCST).
Question 2: What are Liquid Crystals? Name its two types.
Answer:
Liquid crystals are substances that show properties between liquids and solid crystals.
Types of liquid crystals:
Thermotropic liquid crystals – depend on temperature.
Lyotropic liquid crystals – depend on concentration of solvent.
Question 3: What is Surface Tension and Interfacial Tension?
Answer:
Surface tension:
The force acting on the surface of a liquid that tends to minimize its surface area.
Interfacial tension:
The force existing between two immiscible liquids, such as oil and water.
These properties are important in emulsions and drug absorption.
SECTION B – Long Answer Section
This section requires detailed explanations of solubility, complexation, and buffer systems in pharmaceutical preparations.
Question 1: Describe Solubility of Liquids in Liquids.
Answer:
Solubility of liquids refers to the ability of one liquid to dissolve in another liquid.
Types:
Completely miscible liquids
Example: Alcohol + Water
Partially miscible liquids
Example: Phenol + Water
Immiscible liquids
Example: Oil + Water
Factors affecting solubility:
Temperature
Nature of liquids
Pressure
In pharmacy, solubility is important for drug formulation and drug delivery systems.
Question 2: Describe Classification of Complexation.
Answer:
Complexation occurs when molecules form complex structures with metal ions or other molecules.
Types of complexes:
Metal ion complexes
Example: Chelates with EDTA.
Organic molecular complexes
Example: Charge transfer complexes.
Inclusion complexes
Example: Cyclodextrin complexes.
Applications:
Improve drug solubility
Increase drug stability
Enhance drug absorption.
Question 3: Define Buffer Isotonic Solution and Methods of Adjustment of Tonicity.
Answer:
A buffer isotonic solution maintains both constant pH and osmotic pressure similar to body fluids.
Types of solutions:
Hypertonic: Higher osmotic pressure than body fluids.
Hypotonic: Lower osmotic pressure than body fluids.
Methods to adjust tonicity:
Cryoscopic method
Sodium chloride equivalent method
White–Vincent method.
SECTION C – Descriptive Section
This section tests deeper knowledge of pharmaceutical physical chemistry such as adsorption, protein binding, HLB scale, and surface phenomena.
Question 1: Discuss Protein Binding and its Significance.
Answer:
Protein binding refers to the attachment of drugs to plasma proteins such as albumin in blood.
Significance:
Influences drug distribution.
Affects drug half-life.
Controls drug activity and elimination.
Only free drug molecules show pharmacological activity.
Question 2: Define Adsorption and Types of Adsorption.
Answer:
Adsorption is the accumulation of molecules on the surface of a solid or liquid.
Types of adsorption:
Physical adsorption (Physisorption)
Weak intermolecular forces.
Chemical adsorption (Chemisorption)
Strong chemical bonds formed.
Applications:
Drug purification
Chromatography
Gas masks.
Question 3: Explain HLB Scale.
Answer:
HLB (Hydrophilic-Lipophilic Balance) scale measures the balance between water-loving and oil-loving parts of surfactants.
HLB range: 0–20
Low HLB → Oil soluble surfactants
High HLB → Water soluble surfactants
Applications:
Emulsion formulation
Selection of surfactants
Drug delivery systems.
