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Pre-AP Chemistry Notes: Solutions
I. Types of Mixtures (p. 395 – 399) Ch. 13 Solutions
A. Solution– homogenous mixture of 2 or more substances in a single phase
1. Components of Solutions
a. Solute - substance being dissolved --usually lesser amount
b. Solvent – dissolving medium --usually present in greater amount
c. Examples
2.Types of Solutions
air
O2 gas and N2 gas
gas/gas
soda
CO2 gas in water
gas/liquid
seawater
NaCl in water
solid/liquid
brass
copper and zinc
solid/solid
3. Characteristics of Solutions
a. Have small particles (ions or molecules)
b. Are transparent
c. Do not separate
d. Cannot be filtered
e. Do not scatter light.
4. Electrolytes
a.Substance that dissolves in water to produce a solution that
conducts electricity
1) Dissociation separation of an ionic solid into aqueous
ions
b. Ionic compounds (NaCl)
c. Polar cmpds (HCl & other acids)
1) Ionization - breaking apart of some polar molecules into
aqueous ions
5. Nonelectrolytes
a. Substance that dissolves in water to produce a solution that doesn’t
conduct an electricity
1) Molecular Solvation - molecules stay intact
b. Molecular cmpds (sugar)
B. Suspensions (not a solution)
1. Characteristics
a. Have very large particles (1000x larger than atoms)
b. 1000+ nm
c. Settle out
d. Can be filtered
e. Must stir to stay suspended
2. Examples of Suspensions
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Whole Blood (with platelets, rbc’s, wbc’s & plasma)
Muddy water
Calamine lotion (for poison ivy)
C. Colloids (not solutions)
1. Characteristics
a. Have medium size particles
b. 1nm to 1000 nanometers
c. Cannot be filtered
d. Separated with semi-permeable membranes
e.Scatter light (Tyndall effect)
2. Examples of Colloids
paints, mud (sol) , Jello (gel) Milk, mayonnaise, plasma (liquid
emulsion), Whipped cream (foam), Smoke, car exhaust (solid aerosol)
Fog, clouds (liquid aerosol), Cheese, butter (solid emulsion)
II. The Solution Process (dissolution = dissolving)
A. Rate of dissolution – what effects how fast something dissolves?
1. Size of solute
a. Increase surface are of solute – crush the solute – dissolution (the
process of dissolving) occurs on the surface of the solute
2. Motion of solvent
a. Agitate the solution – stir it- helps to disperse the solute particles
b. opposite for a gas!
3. Temp of solvent
a. Heat the solvent – increases KE & helps to separate solute
particles from each other
b. opposite for a gas!
4. pressure
a. No effect on solubility of solids or liquids in a liquid
b. Gas in contact w/ surface of liquid & some gas is dissolved into the
liquid while some gas also escapes the liquid until equilibrium is
reached
c. If you change the pressure a new equilibrium is reached
d. Increasing the pressure on the gas (solute) causes more molecules
to collide w/ the surface of the liquid so more gas molecules
become dissolved in the solvent until a new EQ is reached at
the new pressure----Le Châtelier’s (Le Who?) Principal (apply a
stress to a system in EQ & it will eventually reach a new EQ)
e. Henry’s Law (of gas dissolved in a liquid)
1) The solubility of a gas in a liquid is directly proportional to its
pressure above the liquid (temp remains constant)
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SOOOOOOOOOOO… if the pressure of the gas above
the liquid increases then the solubility of the gas increases
Partial pressure blah, blah, blah
B. Solvation – the process of dissolving
1. solute particles are surrounded by solvent particles
2. solute particles are separated and pulled into solution
C. Solubility
1. Amt of substance required to form a saturated solution w/ a specific amt
of solvent at a specific temp
2. Crystallization is the opposite of dissoluton!
3. Solution equilibrium – state where the
rate of dissolution = rate of crystallization
4. p. 404 Chart shows amt of g of solute that can be dissolve in 100 g water
at different temps.
5. Liquids that aren’t soluble in each other are considered immiscible
Liquids that are soluble in each other are considered miscible
D. Saturated solution
1. A saturated solution contains the max amt of dissolved solute at a
specific temp
a. If you add any more solute at that temp it will not dissolve but {sink}
to the bottom
E. Unsaturated
1. An unsaturated solution contains less solute than the max it can hold at a
specific temp
a. All the solute you put in has dissolved & there is still room in the
solution for more solute
F. Supersaturated
1. A solution that contains MORE solute than a normal saturated solution
can hold under the same conditions!
a. Usually prepared by heating the solvent & saturating it, filtering out
any excess solute, then letting the solution cool while being
careful not to disturb it in any way – if you bump it
etc…crystallization begins because it is VERY unstable!
II. Solute-solvent interactions- Like dissolves Like!
A. Ionic compounds dissolve in polar or ionic solvents but not in nonpolar
molecular solvents & nonpolar substances dissolve in nonpolar substances
1. Hydration – forming a solution with water as the solvent
2. Some hydrated ionic solutions when crystallized incorporate some of the
water molecules in their crystals & are then called “hydrated”
B. Soap/Detergent why does it work on everything?
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1. polar “head” with long nonpolar “tail”
2. dissolves nonpolar grease in polar water
C. Heats of Solution
1. Formation of a solution goes hand-in-hand w/ an E change, E can either
be absorbed or released dependent on the solute & solvent (can be a
really small amount)
2. The NET amt of E released or absorbed is the heat of solution (it’s
different for each solute/solvent combo)
a. + if heat is absorbed (it gets cold to the touch)
b. - if heat is released (it gets hot to the touch)
III. Concentration of Solutions--The amount of solute in a solution.
A. Describing Concentration
1. % by mass - medicated creams
2. % by volume - rubbing alcohol used by bio
3. ppm, ppb - water contaminants
4. molarity - used by chemists
5. molality - used by chemists
B. Molarity = moles of solute per liter of solution (not liter of solvent)
C. molality = moles of solute per kg of solvent
D. Dilution- Preparation of a desired solution by adding water to a concentrate.
Moles of solute remain the same. M1V1 = M2V2