Transcript Solutions

Solutions
Definitions

Solution: homogeneous mixture of 2 or
more substances in a single physical state
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Solute: the substance dissolved in the solution
Solvent: the substance the solute is dissolved in
General Properties of
Solutions
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1. solute particles in solutions are very small
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2. solute particles are evenly distributed
throughout the solution
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3. particles in a solution will not separate
under normal conditions
Types of Solutions
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Aqueous solutions: solutions with water as
the solvent.
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Electrolyte solutions: aqueous solutions of
ionic compounds. Ionic compounds dissociate
allowing for the solution to conduct an
electrical charge
Nonelectrolyte solutions: aqueous solutions
of molecular compounds. The solute does not
dissociate.
Solution Concentrations
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Amount of solute in a given amount of solvent
or solution
Molarity (M)
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Most common expression of solution
concentration
M=
Mols of solute
Liters of Solution
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What is the molarity of a solution formed by
mixing 38 grams of potassium hydroxide in
enough water to make 250 mL of solution?
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If I have a 2.5 M sulfuric acid solution, how
many liters of solution will be needed to
obtain 70 grams of sulfuric acid? How many
milliliters?
Molality (m)
Moles of solute
m=
Kilograms of solvent
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Chlorine is often added to water in swimming
pools and to drinking water to keep the water
clear and free of living organisms. What is
the molality of a solution made up of 16.1 g of
chlorine in 5000 g of water?
Mole Fraction (X)
Mole Fraction =
Moles of solute or solvent
Total moles of solution
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What are the mole fractions of the solute and
solvent of the solution prepared by dissolving
50 grams of sodium chloride in 200 grams of
water?
Saturation
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Saturated: solution contains all possible
solute under current conditions
Unsaturated: more solute can be dissolved
Supersaturated: solution contains solute
past the saturation point for the current
conditions
Changing the Concentration of
a Solution (Diluting)
M1V1 = M2V2
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What volume of 18 M sulfuric acid is needed
to create 6 Liters of 3.25 M sulfuric acid?
Solution Formation
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When ionic compounds dissolve in water,
they dissociate
NaCl --> Na+ + ClEach component has an attraction to a
certain part of the water molecules
Solubility
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the amount of solute that will dissolve in a
specific solvent under given conditions
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Three factors that influence solubility:
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Nature of Solute and Solvent
Temperature
Pressure
Factors Affecting Solubility
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Nature of Solute and Solvent:
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"likes dissolve likes"
polar will dissolve polar
nonpolar will dissolve nonpolar
Ionic compounds are polar, so they will always
dissolve in water.
Factors Affecting Solubility
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Temperature:
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with gas-liquid solutions, solubility decreases as
temperature increases
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with solid-liquid solutions, solubility increases as
temperature increases
Factors Affecting Solubility
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Pressure
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in a gas-liquid solution, solubility increases as
pressure increases
Factors Affecting Dissolving
Rate
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Surface Area
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the amount of area exposed to the solvent
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Stirring
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Temperature
Colligative Properties
of Solutions
-depend upon the concentration
of solute in the solution.
Vapor Pressure Reductions
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Vapor pressure - the gas pressure resulting
from vapor molecules over a liquid.
As concentration increases, vapor pressure is
reduced.
Boiling Point Elevation
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As concentration increases, boiling point
increases.
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Relates back to vapor pressure.
Boiling point is the temperature where the vapor
pressure of a liquid is equal to external pressure
on its surface.
ΔTb = Kbm
Kb=molal boiling point constant
m = molality
Boiling Point Elevation
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39 grams of sodium chloride are added to
500 mL of water. What will the boiling point
be?
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While cooking some noodles, Pete adds salt
to the water (3.25 Liters) as he heats it. How
many grams of salt did he add if the boiling
point of the solution was 101.3˚C?
Freezing Point Depression
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Freezing point is the temperature at which
the vapor pressure of liquid and solid phases
is the same
ΔTf = Kfm
Kf = molal freezing point constant
m = molality
Freezing Point Depression
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How many grams of salt would be needed to
reduce the freezing point of 2 kg of water to
-15˚C?