Solubility Flashcards
what is solubility
the max concentration of a particular solvent that may be achieve under given conditions when dissolution process is at equilibrium
solubility vs miscibility
solid in liquid vs liquid in liquid
when is solution unsaturated
when the solute fully dissolves in solution and more could still dissolve
when is solution saturated
when no more solute can dissolve (at a given temp)
when is solution supersaturated
when it has an excess (higher concentration that saturation) of solute which results in an unstable solution
when does solute begin to precipitate
when the solution is supersaturated
what is molar solubility
the max amount of the compound that can dissolve in the solvent aka the molarity of the saturated solution
what is the process of making a compound soluble
- intermolecular forces between solute molecules are broken to make individual solute molecules
- intermolecular forces between solvent molecules are broken to make space for solute
- new solute-solvent intermolecular forces are formed
decreasing order of IMF strength
ion-ion>ion>dipole>H-bond>dipole-dipole>ion-induced dipole>dipole-induced dipole >LDF
what is an electrolyte
a substance that produces ions when dissolved in water
when does dH favour dissolution
if the eergy released in forming solute-solvent interactions > the energy required to break solvent-solvent and solute-solute interactions
when is dissolution entropically favoured?
if entropy increases (ie if the solute disperses without increasing order)
- unfavoured if entropy decreases (ie ordered structures are formed)
what must happen with the electrolytic interactions for solubility
for ionic compounds to be soluble, the electrostatic interactions within the crystal lattice must be disrupted
ion water interactions endothermic or exothermic
weak water-ion = dissolution = endothermic
strong = exothermic
dG for solution formation
negative
what is solubility equilibria
when an incompletely-soluble chemical is added to water, some spontaneously dissolves until an equilibrium between the bulk chem and dissolved chem is reached = saturation
what is Ksp
the solubility equilibrium constant
what is the common ion effect in solubility
the solubility of a slightly soluble ionic compound is lowered in the presence of a common ion
how cna the common ion effect be used
- to deliberately lower the solubility of certain salts for the purpose of separating them out of solution
- can shift solubility equilibrium to cause precipitation
what is a precipitate
the insoluble product of a reaction of soluble reactants
when do precipitates form
when the concentration of solution is higher than solubility = supersaturation
what is Q for solubility
the ion product
how do equilibrium changes affect precipitation
forward shift = precipitation
reverse shift = dissolution
Q>Ksp
supersaturation = precipitation should occur
Q+Ksp
saturated
Q<K
unsaturated = dissolution (precipitation can’t occur)
what are results of simultaneous equilibria
reactions between solute ions and other species
- acid base reactions and complex ion formation
what are complex systems
when there’s more that one ion in solution with small ksp values with another ion -> multiple possible solubility equilibria
what is fractional precipitation
a technique where 2+ ions in solution are separated by the addition of a reagent
- 1 is precipitated while the others stay in solution
what is required for fractional precipitation
significant differences in solubilities/Ksp values of substances being separate and slowly adding the concentration of the solution of the precipitating reagent
what is qualitative cation analysis
selectively precipitating the 1st group of cations then moving on to the rest, so the precipitates separate and dissolved medal ions can be individually identified by adding anions
what is the goal of qualitative cation analysis
to identify the cations present in a mixture but does not give info on quantities
how does ph affect solubility
ph can affect solubility of a salt if the ion is a weak acid/base since some salts have acidic or basic properties, with shifts in pH affecting solubility
