chapter 12: solutions
chapter 12: solutions
}}formation of solutions!}}
- dissolution: (dissolving) each solute particle is completely surrounded by solvent (h2o) particles
- solute: soluble covalent compounds or ionics
- to dissolve in water → polar
- dissociation: soluble, ionic compounds separate into ions (electrolytes, conductive*)
when dissolved!
three ways to dissolve a solid more quickly!
stir: (shake, agitate)
- solute comes in contact with solvent more often
decrease particle size: (grind)
- solute dissolves faster with more surface area
heat:
- particles moving aster more forceful collisions
- heat increases solubility of solids
}}solubility}}[mass (or number of mols) of solute / volume of solution/solvent]
factors affecting solubility
temperature
- solids dissolve better in warmer temperatures
- gases dissolve better in cooler temperatures
pressure
solids dissolve easily in lower pressures
gases dissolve easily in higher pressures
- this is HENRY’S LAW
}}saturation}}
**use solubility chart/curve
saturated: solution where is has the max amount of solute at a particular temperature
- (on line)
unsaturated: solution with less than the max amount of solute
- (under the line)
supersaturated: solution with more than the maximum amount of solute
- (above the line)
- increase temperature so you can dissolve more and then cool it back down
- created by
- dissolve solute in warm solution, cool slowly (solid stays dissolved)
- destroyed by
- adding seed crystal (small piece of original solute)
- stirring or shaking
difference between supersaturated solution and max amount of solution is what precipitates out
- left with → solid → saturated solution** (check this)*
}}concentration}}
expresses how much solute is dissolved in solvent
- concentrated: lots of solute
- dilute solution: only a little solute, compared to solvent
}}molarity (M)}}
moles of solute (n) per liter of solution (V)
M = (n/v) = (moles solute/liters of solution)
**dependent on temperature because volume of solution would change slightly
}}molality (cursive small ‘m‘)}}
moles solute per kilogram of solvent
m = (moles of solute / kg of solvent)
**not dependent on temperature!
}}parts per million (ppm) and parts per billion (ppb)}}
used for expressing very small concentrations, particularly for containments in environment
ppm = [ mass of solute (g) / vol of solution (mL)] * 10^6 (million)
ppb = [mass of solute (g) / vol of solution (mL)] * 10^9 (billion)
dilution
a dilute solute can be made by adding more solvent to a concentrated solution
- amount of solute stays the same
- \
# of moles of solute stays the same
serial dilution!
}}colligative properties}}
- show how solutions behave differently than pure solvents
- depends of number of solute particles in solution, not type
- changes are more extreme when solutions are concentrated (more particles) rather than dilute
lower vapor pressure
solute particles inhibit solvent from escaping as gas
- less gas → less pressure
boiling point elevation
solute particles make it more difficult for solvent to escape as gas
more energy needs to escape → higher temperature to boil
determining ΔBP: ΔT = (i)(Kb)(m)
ΔBP - change in temperature, not new boiling point
i - # of disassociated particles
VAN’T HOFF FACTOR
i for all molecular compounds equals one!!
Kb - boiling constant, unique for each constant
m - molality: moles solute/kg solven
freezing point depression
solute particles prevent pure solvent from forming
cold temp needed to form solid
determining ΔFP: ΔT = (i)(Kf)(m)
ΔT - change in freezing point
i - # of particles
Kf - freezing constant
m - molality
osmotic pressure
osmosis: the movement of H2O through semi-permeable membrane
increases as the difference in concentration increases
* applying force to stop water from moving across the membrane
- force is known as osmotic pressure