Flashcards in Chapter 9: Solutions Deck (27):
What is solvation/dissolution?
The interaction between solvent and solute molecules: hydration when the solvent is water. Involves breakdown of intermolecular forces between solute and solvent molecules and forming forces between them
When is solvation exothermic? Endothermic?
Exo when solute-solvent interactive forces are stronger than original forces - favored at low temp. Endo when new interactions are weaker - favored at high temp (most dissolutions)
What happens when new interactions have same energy of prior interactions
Enthalpy change for the dissolution is close to zero - approximate the formation of an ideal solution
What happens to entropy in dissolution?
Always increases - entropy of solvent molecules decrease as they become restricted, but this is overcome by large entropy increase of solvent being freed from lattice
In general, when are solutes considered soluble? What are sparingly-soluble salts.
When they have a molar solubility above 0.1M. When solutes dissolve minimally (under 0.1M)
What molecules are always soluble?
Those containing ammonium, alkali metals, nitrate and acetate salts
What is a complex ion/coordinate compound?
Involves at least one electron pair donor (ligand) and a cation held together with coordinate covalent bonds
What is chelation?
When one ligand is able to form multiple bonds with the central cation
Difference between solubility and saturation?
Solubility - the amount of solvent in solution
Saturation - maximum solubility of a solute at a given temp
How to determine mole fractions of compounds?
For a mixture: moles of component divided by total moles of all compounds
What is molality of a solution equal to?
Moles of solute divided by kilograms of solvent. Approximately equals molarity at 25 degrees celsius, as water has a density of 1kg/L
M1V1 = M2V2
where M is molarity and V is volume
Solubility product constant formula? Does not include?
Ksp = [A^n+]^m [B^m-]^n, for an ionic compound with the formula A_mB_n that is saturated and at equilibrium.
Pure solids or liquids
Gas solute Ksp with higher temp? higher pressure?
Aq solute Ksp with higher temp?
What is the ion product? What do its values mean when compared to Ksp?
Same formula as Ksp, just used to calculate at any time (not just at equilibrium). Same as Q is to Keq. If IP is less than Ksp, solution is unsaturated, if greater than Ksp the solution is beyond equilibrium (supersaturated). If equal, it is saturated
What is molar solubility?
The molarity of solute in a saturated solution. For calculations, make this x, dissociates into x and 2x etc
What is the formation constant for a complex ion? What does the formation of these complexes lead to?
The constant for the formation of an aqueous complex ion from two aqueous solutes in solution. Makes the ions significantly more soluble
What is the common ion effect?
The reduction in molar solubility of a salt due to the presence of another salt which contains similar constituent ions. Ksp remains constant
What are colligative properties?
physical properties of solutions that are dependent on the concentrations of dissolved particles, but not on the chemical identity of the dissolved particles.
Four examples of colligative properties?
Vapor pressure depression, boiling point elevation, freezing point depression and osmotic pressure
What does Raoult's law account for?
As solutes are added to solvent, the vapor pressure of the solvent decreases proportionally (as solute molecules block the evaporation of solvent molecules, but not their condensation)
Raoult's law formula?
When does it only hold true?
Pa = Xa * Pa naught, where Pa is vapor pressure of solvent A, X is the mole fraction of solvent A in solution, and Pa naught is the vapor pressure of pure solvent A.
True when the attraction between molecules of the different components of the mixture is equal to the attraction of molecules of any one component
What happens to the BP of a solvent when a nonvolatile solute is added?
Formula to find the extent of this?
What is the van't Hoff factor?
delta(Tb) = (i)(Kb)(m), where the increase in boiling point equals the van't Hoff factor (i) * the proportionality constant for the specific solvent * the molality of the solution.
Number of particles a compound dissociates into (eg. 2 for NaCl, 1 for glucose)
Why does dissolving solute in solution decrease the freezing point?
The presence of solute particles interferes with the formation of lattice arrangements of solvent molecules required for solidification. Eg, why we salt icy roads
Formula for the extent of freezing point depression?
delta(Tf) = (i)(Kf)(m), where i is the van't Hoff factor, Kf is the proportionality constant characteristic of each solvent, and m is molality of the solution
What is osmotic pressure?
The pressure generated by solutions in which water is drawn into a solution