MP2 L4-6 Physical and Chemical Properties of Solutions

Solution

A homogenous molecular dispersion of solute dissolved in solvent

Ideal solution

Complete uniformity of intermolecular forces in a solution

Real solution

Forces of interaction are unequal

Colligative properties

the alteration of the properties of pure solvent die to the no of solute species with the solution

Relate to the absolute no of species as opposed to the nature of the species

What are the colligative properties

Lowering of vapour pressure

Boiling point elevation

Freezing point depression

Increased osmotic pressure

What happens during dissolution of a non volatile solute in a solvent

Reduce the vapour pressure of. a liquid as the mole fraction increases

What happens vapour pressure when 2 volatile solvents are mixed

Vapour pressure will be the sum of the weighted mean of each solvent

What law do ideal substances obey

Raoults law

Raoults law

The vapour pressure of a solution is proportional the the mole fraction of solvent

Osmotic pressure

Pressure that must be applied to a solution to prevent the movement of solvent into it when solution and solvent are separated by a semi permeable membrane

Isotonic

Equal concentration of dissolved species inside v outside the cell

Hypertonic

Higher no of dissolved species outside cell v inside

Hypotonic

Lower no of dissolved species outside cell v inside

i Factor

Factor which accounts for the deviation of colligative property due to the electrolyte nature of the solute

What can excessive consumption of solvent be

Dangerous

What must large volumes for ophthalmic delivery be

Isotonic

What does depression of freezing point play a role in

Physiology of cold blooded animals

What can reducing vapour pressure prevent

Formulations from drying out

Buffer

Solutions of weak acids and their conjugate bases that resist changes in pH

What is pH buffer defined by

pKa and the ratio of acid to base

What does buffer capacity based on

Conc of buffer components

What should the conc of buffer do

Maintain pH of the dosage form without affecting the pH of the body compartment following admin

Percipitation

Process by which a solute dissolved in a solvent loses its a affinity for solvent and reverts to its solid form yielding a solid dispersed in a liquid

What does precipitation do to solution

Cloud it

What is solution the reverse of

Dissolution

Causes of percipitation

Solid state changes

Temp

Solute

Solvent

pH

Incompatible species

Chemical degradation

Excessive addition

Mixing a solvated cation and anion =

Percipitation

Chelation

Relates to the interaction between a metal atom or ion and another species

Interface

Boundry between 2 phases

Absorption

Penetration into the bulk of a phase

Adsorption

Process of accumulation at an interface

Types of adsorption

Physical

Chemical

Factors that affect adsorption

Solute conc

Temp

pH

Solubility of adsorbate

Nature of adsorbent

What does an increase in conc do to adsorption

Increase

What does a suppression in ionisation do to adsorption

Increase

Solubility v adsorption

Inversely proportional

Extent of adsorption is proportional to

Surface area

What does an increase in temp do to adsorption

Decrease

Leeching

Loss of materials from the packaging into the drug solution

Rheology

Study of deformation and flow of matter

Viscosity

resistance to flow