Theory Flashcards
What is a solution?
A homogeneous mixture
e.g liquid or solid phase with more than one component
What is the solvent and solute?
Solvent: component in excess
Solute: minor components
Describe liquids
interaction energy ≈ kinetic energy
NO long range order
Define an equillibrium
Chemical potentials of participating species are constant
What is fugacity?
An effective pressure to correct fot non-ideality
What does Raoult’s law imply? When is it approximately valid?
Implies that there is no change in interactions between pure and mixed phases
Approximately valid when component A is mostly surrounded by itself (when A is the solvent)
What does Henry’s law imply? When will it be approximately valid?
Implies interactions before/ after mixing are different
Will be applicable when B is mostly surrounded by other molecules (B is the solute)
What is Osmosis?
Pure solvent and solution separated by semi-permeable membrane (i.e. allows transfer of solvent but NOT solute)
Spontaneous mixing should occur (to form solution in other compartment), however only possible via solvent transport from R to L
What are some applications of Osmosis?
- Water Purification most general lab-scale technique is reverse osmosis.
Solution exerts higher pressure, osmotic pressure, P.
If external pressure, p > P imposed, then pure solvent (water) will be “squeezed out - Plants and animals use Osmosis to control water flow in and out of cells
What is an example of a strongly non-ideal solution?
Electrolytes
Initially: pure salt and water
electrostatic interactions hold the lattice together, H-bonded and non-covalent interactions between water molecules
On mixing: Solvation (specifically hydration) is strong enough to overcome lattice energy
Overall: Strong water-ion interactions are very different from initial interactions
What is an electrolyte?
Any solution that conducts electricity - any solution which dissociates into ionic species in solution
Describe a weak and strong electrolyte
Strong electrolyte: completely dissociated, degree of dissociation is therefore independent of concentration (e.g. NaCl(aq))
* Weak electrolyte: partial dissociation, degree of dissociation is a function of concentration (e.g. CH3CO2H)
What is the Gibbs Energy of Solvation of an ion?
the change in Gibbs energy on going from 1 mole of gaseous ions, to one mole of the solvated ion
What is Born’s approach to ion salvation
It provides an estimation of the electrostatic component of the solvation energy, which arises from the interaction between the charged solute (ion) and the polar solvent molecules.
