F = C - P + 2 (F - critical number/number of degrees of freedom in the system, C - number of components, P - number of phases)
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What is a phase?
A homogeneous, physically distinct portion of a system that is separated from other portions of the system by bounding surfaces
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What are components?
The smallest number of constituents by which the composition of each phase in the system at equilibrium can be expressed in the form of a chemical equation or formula
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What is the number of degrees of freedom?
The least number of intensive variables (e.g. temperature, pressure, concentration, refractive index, density, viscosity) that must be fixed in order to describe the system
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What is an intensive variable?
Variables which are independent of conditions such as temperature, pH, concentration, pressure, density and do not change the equilibrium state of the system
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Describe the phase diagram of water
Y-shaped line. 1 degree of freedom at boundary line (univariant). 2 degrees of freedom in other spaces (bivariant). 0 degrees of freedom at point where all three lines meet (invariant)
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Describe the phase diagram for phenol and water
Under the curve (two phases). Above the curve (one phase). Consolute temperature. Conjugate phases. Tie line - application for PP4 involving use of sodium ions.
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Describe the phase diagram between liquid and solid phases
Temperature against composition (mole fraction). V-shaped. Solid, liquid and crystals. Horizontal line at V point is the eutectic temperature (point at which solid starts to melt)
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What are the pharmaceutical applications of eutectics?
Griseofulvin-succinic acid (acid dissolves, leaving drug in fine suspension/improve bioavailability). Chloramphenicol-urea (more drug dissolved). Sulphathiazole-urea (higher blood levels). Ciacinamide-absorbic acid (vitamins). Emla cream (emulsion).
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Describe drug identification studies
Eutectic temperatures of a substance with various other compounds are generally different even when the original substances have the same melting point
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Describe how to draw a phase diagram using triangular paper
Each side represents a component. Scale 0-100%. Rotate paper clockwise to get to next component. Look at triangle with horizontal lines. Plot points and draw line. Area above line is 1 phase. Area below line is 2 phases (increase in one component)
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Describe Raoult's law
In an ideal solution, the relationship between the partial vapour pressure of each component and the mole fraction of that component in solution is expressed as a product (multiply) - graphs
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Describe Dalton's law of partial pressures
P equals to total of the products (from Raoult's law). P is the total vapour pressure (sum of the partial pressures of the component gases) - positive and negative deviation from graphs
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Describe Henry's law
In non-ideal systems when 1 component is present in another at a very low concentration. Minor component (solute) and major component (solvent) is expressed in the vapour pressure-composition relationship = P solute = k solute X solute (binary graph)
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Other cards in this set
Card 2
Front
What is a phase?
Back
A homogeneous, physically distinct portion of a system that is separated from other portions of the system by bounding surfaces
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