solutions

Question 1

isssues affected by phase equilibria

Answer 1

whether an interface exists between 2 liquids

distribution of a drug between different media

Question 2

how will a substance transfer (phase)

Answer 2

a substance will transfer spontaneously from a phase in which it has a higher chemical potential to a phase on which it has a lower chemical potential

Question 3

what is a phase

Answer 3

the homogenous, physically distinct parts of a system are known as phases. these are separated from one another by interphases e.g. ice, water, water vapour

Question 4

co-existence at phases

Answer 4

gases at equilibrium only one phase
liquid - miscible one phase immiscible 2 phases
solids- each solid is a separate phase unless a solid solution is formed as solutions only have one phase

Question 5

the number of components in a system

Answer 5

the minimum number of independent species necessary to define the composition of all phases present in the system
e.g. ice water water vapour 3 phases one component

Question 6

when does C = no of species

Answer 6

only when there is no chemical reaction

Question 7

degrees of freedom

Answer 7

(F)number of factors which can be varied independently without noticeably altering the number of phases

Question 8

what does phase rule tell us

Answer 8

the number of degrees of freedom for any particular number of components and phases in any system

Question 9

what is Gibbs phase rule

Answer 9

P+F=C+2 at equilibrium
p is no of phases
c is no of component

Question 10

a colligative property depends on the:

Answer 10

properties of the solvent
concentration (mole fraction) of the dissolved substance
number of particles of dissolved substance in the solution

Question 11

4 main colligative properties

Answer 11

vapour pressure lowering
freezing point depression
boiling point elevation
osmotic pressure
(all thermodynamically related to each-other)
osmotic pressure has enormous importance as it contributes to flow of nutrients through biological cell walls and through plants

Question 12

osmosis

Answer 12

tendency of solvent molecules to pass through a membrane from a more dilute toma more concentrated solution

Question 13

what is osmotic pressure

Answer 13

if a solution is seperated from its solvent by a membrane then the excess pressure which has to be applied to prevent the flow of solvent is known as the osmotic pressure (uppercase pi)
osmotic pressure = RTx molarity

Question 14

what is hydrostatic pressure

Answer 14

pressure exerted by a column of aqueous solution or water is called hydrostatic pressure

Question 15

what is reverse osmosis

Answer 15

reverse osmosis is when a pressure (greater than osmotic pressure) is applied to the solution and forces the solvent through the membrane

Question 16

types of membranes

Answer 16

semi permeable- permeable to solvent molecules only e.g. they will allow the passage of water but mot other molecules
biological (selectively permeable) these allow the passage of water and other molecules of low molecular weight but will restrain molecules of higher molecular weight

Question 17

if red blood cells are immersed in solution of greater osmotic pressure than cells content:

Answer 17

water will pass out of cell to reduce chemical potential across cell membrane (cell shrinks)

Question 18

if red blood cells immersed jn solution of lower osmoticpressure than cells content:

Answer 18

water will enter the cell (cell swells) and eventually lysis (cell breakdown) may occur

Question 19

isotonic solutions

Answer 19

solutions between which there is no net flow of solvent when the solutions are prepared by a biological membrane are called isotonic - notably the RBC cell membrane

Question 20

what must the effective osmotic pressure of a solution for injection be

Answer 20

approx same as blood serum
termed tonicity
not always same as osmolality

Question 21

importance of tonicity

Answer 21

injections- effect of surrounding medium on RBC

Question 22

tonicity in regards to osmotic pressure with blood serum

Answer 22

lower>hypotonic>cell swells, haemolysis may result
higher>hypertonic> cells shrink, crenation
same>isotonic>no net flow of liquid

Question 23

relationship between osmotic pressure and rate of infusion

Answer 23

the higher the osmotic pressure the slower the rate of infusion required

Question 24

relationships between colligative properties

Answer 24

as colligative properties are inter related it is impossible to determine one from the other
osmotic pressure is not easy to measure therefore makes use of other colligative properties to calculate e.g. freezing point depression
molality=moles/kg does not change with temp
molarity= moles/L changes with temp

Question 25

freezing point depression

Answer 25

this is the lowering of the freezing point of the solvent by adding a non volatile solute e,g, add salt to roads to drop the freezing point of water in winter delta Tf= Kf x m kf is freezing point constant of the solvent is concentration of solute

Question 26

converting Tf to osmotic pressure

Answer 26

at a given temp, osmotic pressure is proportional to change in Tf also for dilute ideal solutions change in Tf is proportional to concentration

Question 27

what does solubility depend on

Answer 27

pressure, temperature,presence of salts and chemical reactions

Question 28

what is henrys law

Answer 28

``` effect of pressure “the vapour pressure exerted by a gas dissolved in a solvent at constant temperature is proportional to the mole fraction of the gas” pb=KhXb Kh henrys law constant Xa mole fraction of gas pa vapour pressure of gas ```

Question 29

effect of temperature on solutions

Answer 29

as temp increases, solubility of most gases decrease due to the greater tendency for the gas to expand

Question 30

what is salting out

Answer 30

salting out- gases are often liberated out of solution by addition of NaCl or sucrose the solute added extracts the water molecules, reducing the density of the aqueous environment adjacent to the gas molecule

Question 31

micellar solubilisation

Answer 31

if gas molecules can be incorporated into the interior of micelles then this will increase solubility

Question 32

3 divisions of liquids in liquids

Answer 32

immiscible, partly miscible, completely miscible

Question 33

immiscible liquid mixtures

Answer 33

mo solution is formed P+F=C+2 P=2 and C=2 so degrees of freedom =2 temp and conc. can be varied without necissarily changing number of phases

Question 34

completely miscible liquid mixture

Answer 34

solution is formed P(1)+F=C(2)+2 F=3 temp, pressure and conc can be varies without necessarily moving from a single phase system

Question 35

partially miscible liquid mixture & phase behaviour observed (3)

Answer 35

no of phases can me 1 miscible or 2 immiscible behaviour; solubility increases with an increase in temperature, solubility decreases with an increase in temperature, high solubility only at low or high temperatures

Question 36

what is critical temperature

Answer 36

above which both solutions are completely miscible

Question 37

what is the upper critical solution temperature

Answer 37

highest temp at which phase separation occurs exists because the greater the thermal motion overcomes any potential energy advantage in molecules of one type being close together above this temp both are fully miscible

Question 38

lower critical solution temperature

Answer 38

below which they mix in all proportions and above they form two products at low temp two components are more miscible because they form a weak complex at higher temp the complex breaks up and two components are less miscible

Question 39

what is the max value of F for a single component system

Answer 39

(C=1;P=2) therefore F=2

Question 40

systems where vapour phase is ignored and only solid and/or liquid phase are considered are termed

Answer 40

condensed systems

Question 41

eutectic point

Answer 41

represents the lowest temperature at which the liquid solution can exist

Question 42

what does solid dispersions enhance

Answer 42

the solid dispersions enhance the dissolution of poorly soluble drugs the drug is mixed with a freely soluble “carrier” and enhanced dissolution is also related to particle size

Question 43

two main types of solids in solids

Answer 43

an intimate crystalline mixture of one component in the other a solid solute dissolved in a solid solvent to give a mixed crystal, this is a true solid solution

Question 44

intimate crystalline mixtures - eutectic point

Answer 44

the eutectic point is the point at which the liquid and solid phases have the dame composition (eutectic composition) the solid phase is an intimate mixture of fine crystals of the two compounds when a mixture of 2 components with composition E are cooled, A and B crystallise out simultaneously

Question 45

mixed crystals

Answer 45

these involve a solid solute being dissolved in a solid solvent, generally these have minor component inserted into the structure of the host crystal these solid solutions can exhibit higher, lower or unchanged melting behaviour

Question 46

difference between henrys and raoults law

Answer 46

raoults law applied to the solvent in a solution while henrys law applies to the solute in solution

Question 47

raoults law

Answer 47

the relative lowering of vapour pressure is equal to the mole fraction of the solute in solution

Question 48

solutions which obey raoults law are called

Answer 48

ideal solutions

Question 49

solutions which do not obey raoults law are called

Answer 49

real or non ideal solutions, most are this thpe