Physical + Chemical Solution Properties

Question 1

Solution Outline

Answer 1

A molecular dispersion. Clear, no deflecting of life. Solute binds with solvent on the molecular level (1 phase)

Question 2

Vapour Outline

Answer 2

Substance that is liquid at room temperature. Liquid phase in a gas carrier

Question 3

Non-electrolyte solutes characteristics

Answer 3

non-ionisable (doesn’t dissociate to form ions), don’t conduct electricity and it’s colligative properties depends on the no. molecules in solution

Question 4

Electrolyte Solute Characteristics

Answer 4

Ionisable (does dissociate to form ions), conduct electricity and it’s colligative properties depend on no. of ions in solution

Question 5

Ideal Solution Outline

Answer 5

Complete uniformity of molecular forces in solution. Drug and solvent molecules want to interact with each other as much as they want to interact with themselves.

Question 6

Conditions foe Ideal Solutions

Answer 6

Thermoneutral (neither exo/endothermic dissolution), no change in net system volume, drug and solvent have similar structures. The interactions (vapour pressure, surface tension, refractive index and viscosity) are weighted averages of each pure substance (equal influence)

Question 7

Real/ Non-ideal solution Outline

Answer 7

Molecular forces in solution are non-uniform.

Question 8

Positive Deviation of Raoult’s Law Outline

Answer 8

Drug-drug and solvent-solvent interactions are stronger then drug-solvent interactions

Question 9

Negative Deviation of Raoult’s Law Outline

Answer 9

Drug-solvent interactions are stronger then drug-drug and solvent-solvent interactions

Question 10

Colligative Outline

Answer 10

Collection of properties that change together as solute dissolves in solvent.

Question 11

4 Main colligative properties Outline

Answer 11

Vapour pressure lowering, boiling point elevation, freezing point depression and osmotic pressure increase

Question 12

Relationship between vapour pressure and amount evapourated

Answer 12

High vapour pressure = large amount of water evaporated. Lowering of vapour pressure = decreasing amount of solvent evaporated from surface

Question 13

Positive deviation and vapour pressure relationship

Answer 13

Positive deviation = stronger drug-drug, solvent-solvent interactions = higher vapour pressure = more solvent lost

Question 14

Negative Deviation and vapour pressure relationship

Answer 14

negative deviation = stronger drug-solvent interaction = lower vapour pressure = less solvent lose (drug molecules hold solvent in place)

Question 15

Result of adding non-volatile solute to solvent

Answer 15

Increased conc = reduced vapour pressure (negative deviation)

Question 16

Relationship between negative deviation = vapour pressure = boiling point

Answer 16

negative deviation = stronger drug-solvent interactions = decreased vapour pressure = increased boiling point

Question 17

Molal Elevation and Molal Freezing Constant Outline

Answer 17

Constant is different from solvent to solvent. Use molality instead of molarity as weight is used instead of volume due to temperature dependency. Molal elevation and freezing constants for the same solvents are also different

Question 18

Relationship between molal concentration and elevated boiling point

Answer 18

Increased molal concentration = bigger increase in elevated boiling point

Question 19

Relationship between vapour pressure and freezing point

Answer 19

The lower the vapour pressure = the lower the freezing point

Question 20

Relationship between molal concentration and freezing point depression

Answer 20

Higher molal concentration = lower freezing point depression

Question 21

Osmotic Pressure Def

Answer 21

Force solution exerts on solvent preventing solvent from passing through semipermeable membrane and entering solution. Opposes osmosis

Question 22

Relationship between osmatic pressure and molar conc of solution

Answer 22

increased molar conc = increased osmatic pressure

Question 23

Relationship between osmatic pressure and absolute temp (K)

Answer 23

increase in temp = increase in osmatic pressure

Question 24

Van’t Hoff Factor (i) Outline

Answer 24

Numerical value that accounts for electrolytes ability to dissociate when calculating osmotic pressure. i = the number of ions an electrolyte produces when dissociated

Question 25

Relationship between Van't Hoff Factor and osmotic pressure

Answer 25

The larger the Van't Hoff Factor = the higher the osmatic pressure

Question 26

Why might Van't Hoff Factor deviate from expected when measured

Answer 26

Tendency for some dissociated ions to rejoin meaning that they no longer act like independent ions

Question 27

Pharmaceutical Relevance of colligative properties

Answer 27

Understand interactions between solvent and drug. Examples: maintenance of physiological tonicity when admining drugs (prevent irritation and drug precipitation), humectants (excipients that lower vapour pressure = decreasing evaporation), propellants (excipients that increase vapour pressure for aerosols)

Question 28

How drugs alter solution pH

Answer 28

Acidic drugs lower solution pH (release H+ into solution when dissolving) and alkaline drugs increase solution pH (take up H+ ions from solution when dissolving). Changes in pH of drug can effect chemical (ionisation), microbial (optimal growth) and physical (precipitation) stability

Question 29

Buffer Outline

Answer 29

Substance in solution that prevents sharp increase/decrease of pH. Consists of weak acid/base and it's conjugate base/acid in a 1:1 ratio (needs to be at pKa). Acid components donate protons to base added, base accepts prtons from acid added. Net pH remains the same

Question 30

Buffering Capacity Outline

Answer 30

Defined by conc of strong acid/base required to change the pH of 1L buffer by 1 pH unit. Depends on conc of buffer components

Question 31

Buffer excipient considerations

Answer 31

shouldn't alter physiological pH of admin site (irritation), toxicity, pKa and drug + excipient solubility and permiability, chemical stability and patient acceptability

Question 32

Example of a buffer

Answer 32

phosphoric acid (acid) and monosodium phosphate (conjugate base)

Question 33

Precipitation Outline

Answer 33

Solute no longer has affinity for solvent and falls out of solution forming a suspension. Eventually solute settles at bottom as precipitate and solvent = supernate

Question 34

Precipitation Causes

Answer 34

Solid state change (polymorphism), temp change (eg refrigeration), cosolvent dilution, pH change, adding of a new species (eg one of opposite charge to solute), degradation (eg loss of hydrophilic components in molecule) and adding of solute past the point of saturation (always make up subsaturated solutions)

Question 35

Chelation Outline

Answer 35

Binding of an ion to a substance that donates an electron pair. Lowers bioavailability and can act intercation possibilities are changed

Question 36

Chelators as Excipients

Answer 36

Used as antioxidants

Question 37

Adsorption Def

Answer 37

Binding of a substance to a media's interface. 2 types: physisorption and chemosorption

Question 38

Absorption Def

Answer 38

Binding of a substance throughout a phase

Question 39

Leaching Outline

Answer 39

Movement of a subtance from a container into phase it holds. Eg plasticisers from soft pastics (eg bags) into a lipophilic liquid.

Question 40

Physiosorption Examples

Answer 40

Weak Van der Waals, ion-dipole and dipole-dipole interactions

Question 41

Adsorbate def

Answer 41

Substance binding to interface

Question 42

Adsorbent Def

Answer 42

Interface that substance is binding to