solubility & solutions

Question 1

what is a solution?

Answer 1

a homogenous mixture of two or more pure substances, solution consist of particles, molecules or ions~ions0.1-2nm in size dispersed in a solvent

Question 2

what is a solvent?

Answer 2

a susbtance in which a solute is dissolved

Question 3

what is a solute?

Answer 3

a substance dissolved in the solvent

Question 4

what is the definition of solubility?

Answer 4

the maximum amount of solute that dissolves completely in a given amount of solvent at a particular temperature and pressure

Question 5

what is a saturated solution?

Answer 5

-a solution in which no more solute will dissolve (contains the solute at its solubility limit at any given temp and pressure)

Question 6

what is a supersaturated solution?

Answer 6

-a solution where the solute is present in solution above its normal solubility limit

Question 7

what is dissolution?

Answer 7

the process of dissolving a solute in a solvent to give a homogenous solution

Question 8

what is the dissolution rate?

Answer 8

-the rate of the dissolution process which is proportional to the maximum equilibrium solubility

Question 9

what are the different types of solutions?

Answer 9

-liquid in liquid
-solid in liquid
-solid in solid

Question 10

what is stage 1 of the dissolution that occurs hen a solid is added to a liquid?

Answer 10

-the solid is added in its crystalline form in which molecules of the same substance are linked together.
-The link between molecule need to break to release molecules that will then interact with the molecules of the solvent.

Question 11

what is stage 2 of the dissolution that occurs when a solid is added to a liquid?

Answer 11

-the molecules of the solvent rearrange themselves to make space for the solute molecule

Question 12

what is stage 3 of the dissolution that occurs when a solid is added to a liquid?

Answer 12

the solute molecules is inserted in the solvent molecules pocket and new bonds between the solute and solvent are established

Question 13

what happens with the process of solvation?

Answer 13

-a large increase in entropy and many endothermic salvation processes are spontaneous because of the large increase in entropy that occurs when the solute dissolves

Question 14

what happens to the surface area because of the dissolution process?

Answer 14

-regions of solvent form around the solute where solvent molecules move with the solute
-these regions exist because of the interactions between the molecules such as hydrogen bonding, van Der Waals forces and dipole-dipole interactions

Question 15

what is the effect of a bigger surface area on the dissolution process?

Answer 15

-the higher the number of solute-solvent interaction required for dissolution and so there is a lower solubility

Question 16

what factors ca affect the solubility of a drug?

Answer 16

-structural features
-hydration and solvation

Question 17

what are the two aspects of the structural features factor that affects solubility?

Answer 17

1-molecular surface area/molecular weight
2-hydrophobic/hydrophillic ratio and the position of substituents

Question 18

how does molecular surface area affect solubility?

Answer 18

-it determines the number of solvent molecules that can pack around the solute molecule
-linear or branched structure affects the surface area
-boiling/melting point reflect the interactions within the molecules-higher the boiling/melting point=reduced solubility

Question 19

how does molecular weight influence solubility?

Answer 19

-increasing the molecular weight decreases solubility

Question 20

how does the hydrophilic/hydrophobic ratio affect solubility?

Answer 20

-polar and non polar portions of a drug can interact in different ways with the solvent
-the greater the area of the hydrophilic portion relative to the area of the hydrophobic portion the greater the aqueous solubility
-the distribution of the fictional groups can also determine how the molecule interacts with solvent molecules

Question 21

what is solvation?

Answer 21

-the process of binding of solvent to solute molecules

Question 22

what is hydration?

Answer 22

when the solvent is in water

Question 23

what is the bulk structure of water?

Answer 23

-how molecules of water present in a specific orientation
-cations bind to water strongly and retain a layer of water even after a crystal forms

Question 24

what are structure breakers?

Answer 24

-when monovalent/monoatomic cations bind to 4 molecules of water and this modifies the bulk structure of water

Question 25

what are structure makers?

Answer 25

-ions that increase the structured nature of water such as Al3+

Question 26

why is the effect of monovalent cations on water not favoured?

Answer 26

-it affects the organisation of water molecules greatly and this greater disruption requires more energy and the molecules that cause greater disruption would therefore be less soluble

Question 27

non flashcards content

Answer 27

-tables on slide 5 and 6 -solubility product lecture -formulation calculations

Question 28

what are solutions?

Answer 28

-simple formulations in which an active ingredient is fully dissolved in a vehicle and this is also true for all the other ingredients referred to as excipients

Question 29

what are gels?

Answer 29

-semisolid formulations with a high water content which contain a gelling agent that increases the viscosity of the formulation. -Gels can either be clear formulations or may be turbid although clear gels are preferred by patients.

Question 30

what is the most common vehicle used in pharmaceuticals?

Answer 30

water

Question 31

what are the different excipients used for solutions?

Answer 31

-solvents/cosolvents -solubilising agents -flavouring -sweetening -colouring -viscosity enhancers -preservatives

Question 32

what are the different excipients used for gels?

Answer 32

-solvents/cosolvents -solubilising agents -flavouring -sweetening -colouring -gelling agents -preservatives