D1 Medicines: physiochemical properties 1 Flashcards
What is a solution?
A mixture of two or more components that form a homogenous molecular dispersion.
What is a single phase system?
Only one phase i.e. not one system phased into the other
What is a solvent?
The component present in greater amount, usually a liquid.
What is a solute?
The component present in smaller amount, usually a solid or a liquid.
What is a saturated solution?
Where the solute is at the limit of its solubility at a given temperature and pressure.
What are the two kinds of “liquid in liquid” solution?
- completely miscible e.g. ethanol and water
2. partially miscible e.g. water and ether - affected by temperature
What is miscibility?
It is the mutual solubility of components in a liquid in liquid system.
What are the two kinds of “solid in liquid solutions”?
- non-electrolytes (non ionic) e.g. organic molecules such as phenol and sucrose
- electrolytes (form ions in solution) - strong electrolytes are fully ionised over a wide pH range, weak electrolytes ionisation is dependent on the pH
Does molecular structure affect miscibility?
Yes, small change can have a marked change on solubility e.g. benzene and phenol in water
How does solute structure effect solubility?
Increased branching increases the solubility
How do solute substituents effect solubility?
Interactions between a) solute - solute and b) solute - solvent
What is solvation?
Solvation is the process of binding of solvent to solute molecules. If the solvent is water, solvation is called hydration.
What is the “flickering cluster”?
Model generally accepted for structure of liquid water - clusters of water molecules held by H bonds in pools of unbound water molecules without H bonds.
What is the “hydration number”?
The number of water molecules in the first shell during solvation. In most small monoatomic ions e.g. Na+ have 4 molecules bound in the first shell, so hydration no. is said to be 4
