Unit 9 Flashcards
(20 cards)
When does supercooling occur?
When particles of the liquid do not join to form crystals, it is metastable so crystal formation can be prompted easily
What happens in a mixture to melting point?
Typically lowered
Why do hydrates have a vapour pressure?
They have water in them which can escape to the atmosphere
What is efflorescence?
Materials with high vapour pressure lose water easily
What is deliquescence?
Materials with low vapour pressure hydrate easily
What is a saturated solution?
A solution which contains maximum amount of solute dissolved in a solution at a given temperature
What is a supersaturated solution
one that cant exist in contact with the solid its made from
‘whys water a good solvent for ionic molecules?
Its an insulator
its polar
How does charge affect solubility?
High charge means high lattice enthalpy which means interations with the solutions are usually insufficient to overcome the lattice energy so they are insoluble
Water is polar so is very good at dissolving…
other polar solutes
When a hydrate dissolves in water what happens to volume?
Increases because the hydrate will release water
When an ionic drystal dissolves what will happen to volume?
Decrease water will bind to the ions and create hydration spheres which are lower in volume
Why would a positive deviation from Raoults law happen
Molecules escape easier and vapour pressure is higher than predicted
Why would negative deviations from raoults law happen?
molecules escape less easily so vapour pressure is lower than predicted
In liquid and vapour curves what will be on top for positive deviation?
Vapour
In liquid and vapour curves what will be on top for negative deviation?
Liquid
What is a partially miscible solution?
some dissolves but above a certain concentration they aren’t miscible
What should dG and dH be for solids to dissolve spontaneously?
dG negative
dH small
In order for two liquids to mix what should be negative?
dG and dH should be negative
In what solvent would you dissolve naphthalene?
Benzene. Both organic. like dissolves like
