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WaterPolar molecule w/ polar bondsCauses surface tension & ability
to dissolve polar molecules and ionic compounds
Solutions
a.k.a. homogeneous mixtureSolutions can exist in any of the phases of
matter.Gases = Air (Nitrogen and Oxygen)Liquids = Vinegar (Water and Acetic Acid)Solids = Steel (Iron and Carbon)
What happens at the molecular level?
The solvent molecules surround the solute molecules, in a process called solvation.
Random motion of molecules causes mixing
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Ionic compounds
Ions dissociate when they dissolve!This is what allows them to conduct
electricity when dissolvedCalled electrolytes
Heterogeneous MixturesSuspensions - mixture with large particles
that settle out if left undisturbedColloids - mixture with medium size
particles… larger than solution particles, but smaller than suspension particles
Amounts of Solute
Specific amounts of solute can be dissolved at each temperature and pressure.
Unsaturated = more solute can dissolveSaturated = maximum amount of solute
dissolvedSupersaturated = more than maximum amount
is dissolvedAchieved by increasing temperature, adding solute,
then slowly bringing temperature back down.
Sodium acetate demo!
^ supersaturated ^ unsaturated
sToP & tHinK: If you have 20 grams of KNO3 in 100 g of H2O at 50 C, is it unsaturated, saturated, or supersaturated?
1) How many grams of NaNO3 can dissolve in 100 g of water at 10 C?
2) At what temperature can 80 grams of KNO3 dissolve into100 grams of water?
3) How many grams of KNO3 can dissolve into 50 g of water at 40 C?
To Mix or Not To Mix…Not all substance combinations dissolve! Depends on
polarity/charge…
For a solid/gas solute in a liquid solvent:
If it dissolves… soluble
If it doesn’t… insoluble
For a liquid solute in a liquid solvent:
If it dissolves… miscible
If it doesn’t… immiscible
Oil / water
Factors that Affect Solubility
SOLID SOLUTE the temperature = solubility (usually, but
NOT always) the surface area = solubility
GAS SOLUTE temperature = solubility the pressure = solubility(like in the gas in soda pop lab!)
Alka-seltzer demo
Calculating Concentration
1. Molarity (M)
2. percent composition (%)
3. parts per million (ppm)
4. grams/liter (g/L)
Molarity
M = moles of solute / liters of solutionExample: What is the molarity of 5 moles
of iodine dissolved in water, making 50 L of solution?
2 fish / 2 Liter 2 fish / 4 Liter
Molarity looks at the number of solute particles / volume of solution
Percent Composition
percent by mass = (mass of solute/mass of solution) x 100
percent by volume = (volume of solute/volume of solution) x 100
Example: You pack a suitcase that weighs 50 kg. You add 10 kg of t-shirts. What is the percent by mass of t-shirts?
Example: You add 5 mL of acetic acid to 95 mL of water. What is the percent by volume of acetic acid?
Parts per MillionParts per million is a measure of how many
parts of solute are in a million parts of solution.
ppm = (mass solute / total mass of solution) x 106
Imagine a jar that has a million jelly beans in it. (Yummie!) If 14 of the jelly beans were yellow we could say that the yellow jelly beans had a concentration of 14 parts per million.
Melamine audio ->
Grams per Liter
Grams per liter represents the mass of the solute divided by the volume of the solution.
g/L = grams of solute / liters of solutionExample: You have 20 grams of sodium
chloride dissolved in water with a total volume of 5 liters. What is the concentration of NaCl in grams/liter?
Molar Dilutions
Making solutions of lower concentrations from higher concentrations
M1V1 = M2V2
Example: What volume of a 3 M HCl solution is needed to make 2 L of 1 M HCl?
Example: How many liters of 6 M NaOH is required to make 2 L of 4 M NaOH?
Colligative Properties
physical properties affected by the NUMBER of solute particles, NOT the solute identityvapor pressure loweringboiling point elevationfreezing point depression
How would dissolving 1 mole of CaCl2 differ from 1 mole of NaCl in affecting colligative properties?
Club soda demo!