ch 17 Flashcards
homogenous mixture
can be any phase
ex. gas/gas
solution
solute + solvent
colligative properties
physical properties that depend on # of solute particles
- boiling point elevation
- freezing point depression
- osmotic pressure
boiling point elevation
when we add a nonvolatile solute to a solution boiling point increases
nonvolatile solutes dont evaporate easily (sits in and above liquid and prevents liquid from turning to gas)
lowers vapor pressure and increases boiling point
osmotic pressure
pressure required to stop the flow of solvent from low to high concentration
when osmosis stops, same osmotic pressure = isotonic
pi = iMRT
solubility rule
like dissolves like
nonpolar/nonpolar
polar/polar
thermodynamics of solute formation
- expanding solute –> break up and expand –> delta H (+)
- expand solvent –> (delta H (+)
- mix solute and solvent usually delta H (-)
factors affecting solubility
saturation of soln
temperature
pressure
how does saturation affect solunility
saturated = soln holding max # of solute
unsat. = soln holding less than max amount
supersat = soln holding more than max solute
how temp afffects solubility
solids : as temp increases solubility increases
gases : as temp increases KE of gas molecules increase and thus they can escape the liquid more, so solubility decreases
how does pressure affect solubility
henry’s law
P = kmX (x= mole fractin
when pressure increases. more gas dissolves into liquid
vapor pressure
pressure exerted by vapor of a liquid or solid
volatile : high VP, evaporates easily, low BP
nonvolatile: low VP , doesn’t evPORATE easily
what happens if you mix a volatile solvent and a nonvolatile solute
BP increases and VP decreases
gas is trapped by solute
raoult’s law
Psoln = Xsolvent*Psolvent
only solvent contributes to VP
what happens if you mic a volatile and volatile
both contribute to VP