13-1 Flashcards
Solutions are
homogeneous mixtures of two or more pure substances
Solution formation is driven by
natural tendency toward mixing (amount of disorder increases)
& attraction by intermolecular forces
Mixing causes
more randomness (disorder) in the position of the molecules, increasing entropy
Solute–Solute attractions must
be overcome to disperse these particles when making a solution.
∆H > 0
Solvent–Solvent attractions must
must be overcome to make room for the solute.
∆H > 0
Solvent–solute attractions occur as
particles mix
∆H < 0
When ∆H < 0, solutions…
form, regardless of randomness change (exothermic)
When ∆H > 0
|∆Hsolute + ∆Hsolvent | must be close to |∆Hmix|
and randomness (disorder) must increase significantly (endothermic)
Most ionic compounds
do dissolve in polar solvents (ex. water) b/c
∆Hsolute + ∆Hsolvent | ≈ |∆Hmix|
& entropy increases greatly (endothermic)
Saturated solution definition
the rate of the opposing processes is equal. The solution contains the maximum amount of solute that can dissolve at a given temperature.
Unsaturated solution defination
contains less solute than the saturated solution
supersaturated solutions definition
the solvent holds more solute than is normally possible at that temperature. These solutions are unstable
In a solution, the solute
dispersed uniformly throughout the solvent.
Ionic compounds
do NOT dissolve in non-polar solvents b/c
|∆Hsolute + ∆Hsolvent |»_space; |∆Hmix| and entropy increases greatly (endothermic)
HCl dissolves in water (covalent)
despite the decrease in disorder b/c ∆H «<0 (exothermic)
