Ceutics Flashcards
What will you come to know about in this chapter?
Solubility expression, mechanisms of solute-solvent interaction, ideal solubility parameters, solvation and association, factors influencing drug solubility, diffusion principles in biological systems
These objectives guide the learning outcomes of the chapter.
What are the main aspects of solubility discussed in this chapter?
Solubility of gas in liquids, liquids in liquids, Raoult’s Law, critical solutions temperature (CST), distribution law
These aspects cover both theoretical and practical applications of solubility.
What is Raoult’s Law?
A principle that relates the vapor pressure of a solvent to the concentration of solute
It applies to ideal solutions and is essential for understanding solubility in mixtures.
What does the Critical Solutions Temperature (CST) indicate?
The temperature at which two components of a mixture become completely miscible
CST is crucial in understanding solubility behavior in various temperatures.
What is the Distribution Law or Nernst’s distribution law?
A law that describes how a solute distributes itself between two immiscible solvents
It has applications in extraction processes and limitations in certain conditions.
Fill in the blank: Factors influencing the _______ of drugs are discussed in this chapter.
[solubility]
What are the mechanisms of solute-solvent interaction?
Interactions such as hydrogen bonding, van der Waals forces, and ionic interactions
These interactions play a critical role in determining solubility.
What is meant by ‘ideal solubility parameters’?
Quantitative measures that predict how well a solute will dissolve in a solvent
They help in formulating drugs and understanding solubility.
What are the principles of diffusion in biological systems?
The movement of molecules from an area of higher concentration to an area of lower concentration
This principle is essential for drug delivery and absorption.
What types of solubility are explored in this chapter?
Solubility of gas in liquids, liquids in liquids
Each type has unique characteristics and applications.
What are the applications of Distribution Law?
Used in extraction processes, drug formulation, and pharmacokinetics
Understanding these applications is vital for practical uses in chemistry and pharmacology.
What are the limitations of Distribution Law?
Assumes ideal behavior, may not apply to highly polar or ionic compounds
Recognizing these limitations is important for accurate predictions in real-world scenarios.
What is solubility defined as in quantitative terms?
The concentration of solute in a saturated solution at a particular temperature
How can solubility be qualitatively defined?
The spontaneous interaction of two or more substances to form a homogeneous molecular dispersion
What factors affect the solubility of a solute?
- Physical and chemical properties of solute and solvent
- Temperature
- Pressure
- pH of the solution
- Particle size of the solute
Why is understanding solubility important for pharmacists?
It is a key parameter affecting the formulation of dosage forms
What are some phenomena that make solubility an important criterion?
- Choice of solvent for liquid formulation
- Dissolution of drugs
- Bioavailability of drugs
What is a solution?
A system in which solutes are completely dissolved in solvent and remain present at the molecular size
Define solute.
The substance which is dissolved in the solvent
Define solvent.
The component in which solute is dissolved
What is a saturated solution?
A solution in which solute is dissolved up to its maximum limit of solubility at a given temperature and pressure
What is an unsaturated solution?
A solution in which dissolved solute is in a concentration below the required amount necessary for complete saturation
What is a supersaturated solution?
A solution which contains more of the dissolved solute than it would normally contain in a saturated state
How is solubility expressed according to the United States Pharmacopeia (USP)?
As parts of solvent required for one part solute
List the solubility classifications provided by the USP.
- Very soluble
- Freely soluble
- Soluble
- Sparingly soluble
- Slightly soluble
- Very slightly soluble
- Practically insoluble
What principle is used in selecting a good solvent?
‘Like dissolves like’
What happens if the attraction force between solute and solvent (X-Y) is less than that within the solvent (X-X)?
The solvent molecule has a greater affinity for its own molecules than for the solute molecules
Provide an example where a solute is insoluble in a solvent due to strong solvent-solvent attraction.
Benzene is almost completely insoluble in water
What occurs if the attraction between solute molecules (Y-Y) is much greater than between solute and solvent (X-Y)?
The solvent will not be able to break the binding forces between solute molecules
What is required to dissolve sodium chloride in a solvent?
A highly polar solvent such as water
What is the application of barrier in drug movement?
The application involves dissolution of drug from tablets, granules, ointments, and suppositories; release from sustained or controlled release dosage forms; absorption, distribution, and elimination of drug in biological systems.
What governs the movement of drug molecules in biological systems?
Movement is governed by the concentration gradient, moving from higher concentration to lower concentration through biological membranes or barriers.
What is Fick’s First Law of Diffusion?
Fick’s First Law states that the rate of drug transport across a unit cross-section of a barrier (flux) is directly proportional to the concentration gradient.
What is the formula for flux according to Fick’s First Law?
J = -D (dC/dx)
Where J is the flux, D is the diffusion coefficient, C is the concentration, and x is the distance.
What does the negative sign in Fick’s First Law indicate?
The negative sign indicates that diffusion occurs in the direction of decreasing concentration.
What factors influence the diffusion coefficient (D)?
The diffusion coefficient may be influenced by:
* Concentration
* Temperature
* Pressure
* Solvent properties
* Chemical nature of the diffusant.
What does Fick’s Second Law describe?
Fick’s Second Law describes how diffusion causes concentration to change with time.
What is the primary equation for Fick’s Second Law?
∂C/∂t = D ∂²C/∂x²
This equation describes the change in concentration C over time t.
How is the solubility of gas in liquids defined?
The solubility of gas is the amount of gas dissolved in a liquid that is in equilibrium with the pure gas above the solution.
What factors affect the solubility of gas in liquids?
The solubility of gas depends on:
* Temperature
* Pressure
* Salt present
* Chemical reactions
* Micellar solubilization.
How does temperature affect the solubility of gas in liquids?
As temperature increases, the solubility of gas in liquid decreases.
What is the effect of pressure on gas solubility in liquids?
The solubility of each gas at constant temperature is directly proportional to its own partial pressure.
Fill in the blank: The solubility of oxygen in water at 10°C is ______ ml per 100 ml of water.
3.25
True or False: At higher temperatures, more gas remains dissolved in the liquid.
False
What is recommended before opening ammonia bottles?
Ammonia bottles should be cooled before opening and the stopper should be covered with cloth.
What is the significance of heating water to 90°C in distillation?
Heating water to 90°C or higher removes dissolved gases before distillation.
