Podcast
Questions and Answers
What is the temperature at which a minute amount of solid thymol separates out to form a two-phase solid-liquid system in system X?
What is the temperature at which a minute amount of solid thymol separates out to form a two-phase solid-liquid system in system X?
- 13°C
- 29°C (correct)
- 35°C
- 22°C
What is the composition of the mixture at the eutectic point in the salol-thymol system?
What is the composition of the mixture at the eutectic point in the salol-thymol system?
- 34% thymol in salol (correct)
- 50% thymol in salol
- 25% thymol in salol
- 60% thymol in salol
What is the consequence of forming eutectic mixtures in pharmaceuticals?
What is the consequence of forming eutectic mixtures in pharmaceuticals?
- They may become less effective at ambient temperature
- They may become more stable at ambient temperature
- They may become more soluble at ambient temperature
- They may liquefy at ambient temperature (correct)
What is the eutectic temperature of the 1:1 mixture of lidocaine and prilocaine?
What is the eutectic temperature of the 1:1 mixture of lidocaine and prilocaine?
What happens as system X is progressively cooled?
What happens as system X is progressively cooled?
What is the lowest temperature at which a liquid phase can exist in the salol-thymol system?
What is the lowest temperature at which a liquid phase can exist in the salol-thymol system?
What is the primary purpose of the phase rule in thermodynamics?
What is the primary purpose of the phase rule in thermodynamics?
What does the number of degrees of freedom represent in the context of phase equilibria?
What does the number of degrees of freedom represent in the context of phase equilibria?
What is the primary characteristic of a one-component system in terms of phase equilibria?
What is the primary characteristic of a one-component system in terms of phase equilibria?
What is the purpose of a phase diagram, such as the one shown in Figure 2?
What is the purpose of a phase diagram, such as the one shown in Figure 2?
What is the significance of the phase rule in understanding the behavior of a system at equilibrium?
What is the significance of the phase rule in understanding the behavior of a system at equilibrium?
What is the primary purpose of a tie line in a two-component system?
What is the primary purpose of a tie line in a two-component system?
What is the relationship between the number of degrees of freedom and the number of intensive variables in a system?
What is the relationship between the number of degrees of freedom and the number of intensive variables in a system?
What is the minimum number of phases present in a two-component system at equilibrium?
What is the minimum number of phases present in a two-component system at equilibrium?
What happens to the composition of the phases when the temperature of a two-component system is increased?
What happens to the composition of the phases when the temperature of a two-component system is increased?
What is the purpose of the phase rule in a two-component system?
What is the purpose of the phase rule in a two-component system?
Suppose we prepare a system containing 60% by weight of thymol in salol and raise the temperature of the mixture to 50°C. What can be said about the system at this point?
Suppose we prepare a system containing 60% by weight of thymol in salol and raise the temperature of the mixture to 50°C. What can be said about the system at this point?
What is the importance of knowing the composition of each phase in a two-component system?
What is the importance of knowing the composition of each phase in a two-component system?
What is the role of the tie line in determining the weight of each phase?
What is the role of the tie line in determining the weight of each phase?
What happens to the weight of each phase when the temperature of a two-component system is increased?
What happens to the weight of each phase when the temperature of a two-component system is increased?
Flashcards are hidden until you start studying
Study Notes
Phase Equilibria and The Phase Rule
- The phase rule is a relationship that determines the least number of independent variables (e.g., temperature, pressure, density, and concentration) that can be changed without changing the equilibrium state of the system.
- The number of variables that may be changed independently without causing the appearance of a new phase or disappearance of an existing phase is referred to as the number of degrees of freedom.
- The number of degrees of freedom is the least number of intensive variables that must be fixed/known to describe the system completely.
One Component Systems
- A phase diagram for water at moderate pressures is shown in Figure 2.
Two Component Systems
- Importance of Tie line:
- Calculation of the composition of each phase.
- Determination of the weight of each phase.
Phase Diagrams and Eutectic Points
- A system containing 60% by weight of thymol in salol:
- Remains a single liquid until the temperature falls to 29°C, at which point a minute amount of solid thymol separates out to form a two-phase solid–liquid system.
- As the system is progressively cooled, more and more of the thymol separates as solid.
- A system containing salol and thymol:
- The solid phase that separates at 22°C is pure salol.
- The lowest temperature at which a liquid phase can exist in the salol–thymol system is 13°C, and this occurs in a mixture containing 34% thymol in salol.
- This point on the phase diagram is known as the eutectic point, where three phases (liquid, solid salol, and solid thymol) coexist.
Pharmaceutical Importance
- Numerous drugs form eutectic mixtures (solid dispersion), with the consequence that they may liquefy at ambient temperature owing to the melting point decrease characteristic at the eutectic point.
- Example: Lidocaine and prilocaine, two local anesthetic agents, form a 1:1 mixture having a eutectic temperature of 18°C.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
