solubility Flashcards
Define solubility
Solubility is an intrinsic property of a material. It is the maximum amount of solute that will dissolve in a given quantity of a solvent, at a given temperature.
Describe polar solvents and properties affecting solubility
Polar solvents dissolve polar solutes. Solubility of these depends on structural features including:
- ratio of polar:non-polar groups of molecules
- Straight chain alcohols, aldehydes and ketones are slightly soluble in water
- additional polar groups increase solubility
- branching of chains increases solubility
Describe non-polar solvents and give an example
Dissolves non-polar solutes through weak intermolecular attractions and vdW forces.
example: oil in benzene
Describe semipolar solvents and give an example
Intermediate solvents that induce miscibility in polar and non-polar liquids. This can induce a degree of polarity
example: acetone increases solubility of ether in water.
What is a solvation mechanism? What is the universal solvent?
Solvation mechanisms are the way in which a solvent dissolves a solute.
Water is regarded as a universal solvent, where it has a high dielectric constant and is amphiprotic.
What is a dielectric constant?
The extent to which a material can store charge. Increasing polariy is proportional to the dielectric constant.
What is dipole interaction in terms of being a solvent mechanism?
This is the attraction between partial charges of solvents and solutes. Solutes must be polar to compete for bonds of solvent molecules.
Describe H bond formation as a solvation mechanism
Water dissolves phenols, alcohols and other O and N containing compounds that can form hydrogen bonds with water.
How do amphiprotic substances interact as solvents?
Amphiprotic substances are able to break covalent bonds of strong acids and bases, being both a proton donor and acceptor, being an effective solvent for these substances.
Describe solvent-solute interactions of weak acids and bases in water.
weak acids/bases are not completely ionised (solubilised) in water due to hydrogen bonds formed. Addition or a conjugated acid/base will increase the solubility of the substance.
What factors affect gas-in-liquid solutions?
pressure
temperature
electrolytes
chemical reactions
Describe how pressure affects a gas-in-liquid solution and what law governs this
This can be observed using Henry’s law, where the concentration of dissolved gas is proportional to the partial pressure of undissolved molecules times the solubility coefficient.
This is only applicable to dilute solutions at a constant temperature.
Explain the effects of temperature on solubility in a gas-in-liquid solution
As temperature increases, the solubility of gas decreases due to the tendency of gas to expand.
Explain how electrolytes affect the solubility of gas-in-liquid solutions
Gases are released by the introduction of salts due to a greater affinity of electrolytes towards water resulting in a weakening of gas-solvent interactions. This decreases the solubility of gases in liquids.
Describe a liquid-in-liquid system and
the categories of these
These are preparations involving the mixing of 2 or more liquids, and are divided into completely and partially miscble systems.