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Unit 12
MixturesCombination of 2 or more different substances
Heterogeneous mixtures – can see the parts (trail mix)
Homogeneous mixtures – mixture appears uniform (Kool-aid)
Types of Mixtures1. Suspensions2. Solutions3. Colloids
SuspensionHeterogeneous mixtureParticles remain mixed with liquid when stirred but separate spontaneously over time
Example – flour & water
Flour & water
SolutionHomogeneous mixture with even distribution of particles
Can be gas (air) or solid (brass)Most often liquid
Solutes dissolved in solventAqueous solution – water is solvent
ColloidStable heterogeneous mixture
Appears homogeneous to naked eye b/c even distribution
BUT components visible under microscope
Does not settle when left to stand
Separating MixturesDecanting – pour off liquid
Separating MixturesCentrifuge – spin to separate by density
Separating MixturesFiltration – liquid through filter
Separating MixturesEvaporation – leaves behind solid
Separating MixturesChromatography - based on dissolving rates
Separating MixturesDistillation – separate by boiling point
ConcentrationRatio of solute to solventConsistent throughout solutionCalculating concentration
Parts per million (ppm)
Molality (m)
Molarity (M)
g solute1 000 000 g solvent
moles solutekg solvent
moles soluteL solution
Molarity (M)M is read as “molar” or “moles per liter”
Any amount with the same molarity will have the same concentration or ratio of solutes to solvent
So 1 mL of 1 M HCl has the same concentration as 20 L of 1 M HCl
Preparing a SolutionWhen preparing a solution, you must have the correct total volume
1.00 mole solute + 1.00 L solvent DOES NOT equal 1.00 M solution!
Instead you need 1.00 L total solution
So dissolve solute in small amount of solvent and then add more solvent to get the correct total volume of solution
Calculating Molarity0.30 moles of KBr are dissolved in 0.40 L of solution. What is the molarity?
M = 0.30 moles KBr =0.40 L solution
0.75 M KBr
Calculating MolarityWhat is the molarity of a KCl solution that has a volume of 400.0 mL and contains 85.0 g of KCl?
Two problemsGramsmL
Molarity CalculationsHow many grams of CaCl2 are needed to make 625 mL of a 2.0 M solution?
DilutionAdding solvent to solutions to decrease the concentration
Does not change the number of moles of the solute that are present
M1V1 = M2V2
Practice2.0 L of a 0.88 M solution are diluted to 3.8 L. What is the new molarity?
PracticeYou have 150 mL of 6.0 M HCl. What volume of 1.3 M HCl can you make?
SolubilityThe ability of a solute to dissolve in a solvent
Measured in terms of the amount of a solute that will dissolve in a given amount of solvent
Solubility – “Like dissolves like”Polar substances tend to dissolve in other polar substances
Nonpolar substances tend to dissolve in other nonpolar substances
Degree of polarity also mattersMiscible – liquids that are completely soluble in each other
Solubility – “Like dissolves like”Polar + nonpolar doesn’t usually dissolve
Immiscible – 2 or more liquids that do not mix with each other
How can we speed the dissolving process?Shaking or stirring
Increases the surface area contact between the solute & solvent
Increasing the temperatureMore energy available for dissolving
Effects of temp on solubilityID trends
Least solubleMost soluble
Extrapolate data200 g at 50 oC
Precipitate formed from cooling
SaturationThere is a maximum amount of solute that can be dissolvedSaturated solution
Less than that maximum amountUnsaturated solution
More than that maximum amountSupersaturated solution
Colligative PropertiesAny physical effect of the solute on the solvent
Not specific to the solute present but rather caused by the presence of a solute
ExamplesBoiling point elevationFreezing point depression