Solutions

Question 1

Dissolution

Answer 1

-Absorption
-Formulation
-Medicine incompatibilities

Question 2

Absorption

Answer 2

Drugs usually need to be aqueous solution to be absorbed

Question 3

Solute-solvent interactions

Answer 3

Attractive forces between solute and solvent are governed by the molecular structure of the solid and the nature of the solvent

Question 4

Effects of solute structure

Answer 4

• small change in molecular structure
  -addition/ removal of a functional group

Question 5

Which is more polar; phenol or benzene and why?

Answer 5

Phenol is more polar and is more soluble because of the presence of OH- group
Hydrogen bonds can form with water.

Question 6

acid + base»>

Answer 6

salt + water

Question 7

effects of solute structure

Answer 7

1. molecular shape
2. Position of groups on benzene ring

Question 8

Charged functional groups are more hydrophilic or hydrophobic

Answer 8

Hydrophilic

Question 9

Polar solvents

Answer 9

-water
-methanol
-acetic acid

Question 10

Relative permittivity Er - elements

Answer 10

water - 80
chloroform - 5
benzene - 2
(non-polar = much lower relative permittivity)

Question 11

what is relative permittivity?

Answer 11

-Polar solvents dissolve ionic solutes by recuding the force of attraction between oppositely charged ions in crystalline solids; Na2CO3
-Polar solvents can even break covalent bonds
HCl + H2O> H3O+ + Cl-

Question 12

Semi-polar solvents examples

Answer 12

Acetone (Er - 20.7)
Ethanol (Er 24.5)
Dimethyl sulfoxide (Er - 45)

Question 13

explain what are semi-polar solvents

Answer 13

• dissolve polar + non-polar substances
• solvent molecule dipole moment on H-bonding groups enable polar solutes to be dissolved
• semi-polar solvents can induce a degree of polarity in non-polar solvent molecules e.g benzene (is soluble in ethanol)

Question 14

Examples of non-polar solvents

Answer 14

• Alkanes
  -Benzene
• Oils and fats

Question 15

explain non-polar solvents

Answer 15

• Low dielectric constant and lack of H-bonding groups prevent these solvents from dissolving ionic or polar solutes
• unable to break covalent bonds
• dissolve non-polar compounds only
• non-polar solutes are held on solution through van der waals interaction with the solvent

Question 16

what other factors determine solubility?

Answer 16

1. Temperature
2. polymorphism/ solvates/hydrates
3. Particle size
4. pH

Question 17

effect of temperature on solubility

Answer 17

• dissolution is usually an endothermic process
• ^^ temp = ^^ solubility
  -exothermic = less soluble

Question 18

Polymorphism/solvates/hydrates

Answer 18

• crystalline solids can exist as different polymorphs depending on how constituent (substance w 1 or 2 substances miXed together)molecules are arranged
  -Structure also altered by incorporation of solvent molecules (solvates % hydrates
  -less stable polymorphs (metastable); more soluble