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					       Solutions

Homogeneous mixture
Dissolved particles
 remain in solution
        Solutions

Can be in any phase of
 matter
Examples:
                 Air in a hot air balloon

Brass puzzle     Gas solution

Solid solution           Soda
                         Liquid solution
 Two parts of a Solution

Solute-substance that
 gets dissolved
 Two parts of a Solution

Solvent-substance that
 does the dissolving
        Molarity

Method to express
 concentration of a
 solution
         Molarity

Number of moles of
 solute per liter of
 solution (not solvent)
         Molarity

When making molar
 solution, you typically
 use volumetric
 glassware.
        Molarity
Example
4M NaCl – 4 moles
 NaCl dissolved in 1
 liter of solution
         Molarity

M = moles solute
    liter solution
          Molarity
Sample problem # 1
Calculate the molarity of a
 solution that contains 3.65
 g HCl in 2.00 liters of
 solution.
          Molarity
Sample problem # 2
Calculate the mass of
 Ba(OH)2 requires to make
 2500. mL of a 0.060 M
 solution.
         Molality

Another method used
 to express concentration
         Molality

Number of moles of
 solute dissolved in 1 kg
 of solvent.
         Molality

Example
6.3 m KCl in water = 6.3
 moles of KCl dissolved in
 1 kg of water
         Molality

 m = moles solute
     1000 g solvent
m = moles solute
     1 kg solvent
          Molality
Sample Problem # 1
How many grams of KI
 must be dissolved in 500 g
 of water to produce a
 0.060 molal KI solution?
          Molality

Sample problem # 2
Calculate the molality of a
 solution containing 2.5 g
 K2CrO4 in 23.2 g of water.
         Molality
Sample problem # 3
How many grams of H2O
 are needed to dissolve
 41.0 g NaC2H3O2 to make
 a 3.00 m solution?
          Molality
Often used in calculation
 that involve colligative
 properties which are
 physical properties that are
 dependent on the number
 of solute particles.
  Colligative Properties

Properties that depend
 on the concentration of
 solute particles not their
 identity for solutions
  Colligative Properties -
           Types
Lowers the vapor
 pressure
The solution becomes less
 volatile, it does not evaporate as
 easily
With solute   Without solute
  Colligative Properties -
           Types
Freezing point
The freezing point is lower for
 the solution, dependant on the
 concentration and type of solute
  With out solute


With solute
  Colligative Properties -
           Types
Boiling point
The boiling point is higher for
 the solution dependant, on the
 concentration and type of solute
                    More solute




      Some solute


Plain water
  Colligative Properties -
           Types
Osmotic Pressure
Greater the concentration of the
 solution the greater the osmotic
 pressure which can cause cells to
 shrink to swell
 Freezing Pt. Depression

The lower of the
 freezing point of a
 liquid that occurs when
 a solute is dissolved
 Freezing Pt. Depression
The solute particles
 interfere with the
 crystallization process
 therefore lowering the
 freezing point
 Freezing Pt. Depression

Tf = i Kf m
 Freezing Pt. Depression
For nonvolatile,
 nonelectrolytic
 solutions, i is equal to 1
Covalent bond
 Freezing Pt. Depression

For electrolytic
 solutions (ionic
 compounds, i is equal to
 the number ions formed
 Freezing pt Depression

Sample problem # 1
 what is i for NaCl,
 Al2(SO4)3 and
 C12H22O11 ?
 Freezing Pt. Depression
Sample problem #2
If 85g of sugar
 (C12H22O11) are dissolved
 in 392.0g of water, what is
 the freezing point of the
 solution?
  Boiling Pt. Elevation

The increase in the
 boiling point of a liquid
 due to a solute being
 dissolved in the liquid
  Boiling Pt. Elevation

Takes more energy for
 the particles to escape
 to a gas due to
 intermolecular forces
  Boiling Pt. Elevation

 Tb = i Kb m
   Boiling Pt. Elevation
Sample problem # 3
If 85g of sugar
 (C12H22O11) are dissolved
 in 392.0g of water, what is
 the boiling point of the
 solution?
         Solubility
Soluble-when the solute is
 able to dissolve in the
 solvent
Miscible-two liquids
 completely dissolve in one
 another
    Solubility Rule
Like dissolves like
       Solubility Rule

Polar solvents dissolves
 polar solutes
Example: water and
 alcohol, water and salt
        Solubility Rule

Nonpolar solvents
 dissolves nonpolar solutes
Example: gasoline and oil
   3 Types of Solutions

Unsaturated solution-
 solution that contains less
 than the maximum amount
 of solute that will dissolve.
   3 Types of Solutions

Unsaturated solution-
Additional solute will
 dissolve
   3 Types of Solutions

Saturated Solution-
 solution that contain the
 maximum amount of
 solute that will dissolve
   3 Types of Solutions
Saturated Solution
Additional solute will
 not dissolve but settle to
 the bottom
    3 Types of Solutions

Supersaturated solution-
 solution that contains more
 than the maximum amount
 of solute that will dissolve.
    3 Types of Solutions
Supersaturated solution
Additional solute will
 cause the dissolved excess
 solute to crystallize out.
Very rare
        Solubility

Measurement of the
 amount of solute that
 can be dissolved in a
 given amount of solvent
     Solubility Curve

Graph the illustrates the
 solubility of several
 substance at various
 temperatures
  Factors that Effect Solubility

1. Nature of the solvent
 and solute
Like compounds dissolve like
 compounds
Solubility can be predicted based
 on polarity
  Factors that Effect Solubility

2. Temperature
Increase temp., increases
 solubility
For as gas, increase temp.,
 decreases the solubility
  Factors that Effect Solubility

3. Pressure
Doesn’t effect solids or
 liquids
For a gas, increase pressure,
 increases solubility
     Rate of Solution

Measurement in how
 quickly a solute
 dissolves in a solvent
   Factors that Affect the
     Rate of Solution
1. Particle size (crushing)
Smaller the particles the more
 total surface area is exposed to
 the solvent to the faster it
 dissolves
   Factors that Affect the
     Rate of Solution
2. Stirring
Fresh solvent is brought into
 contact with the solute quicker
 so stirring increases the rate
  Factors that Affect the
      Rate of Solution
3. Amount of solute
 already dissolved
The more particles dissolved in
 the solution the slower new
 solute will be dissolved
  Factors that Affect the
     Rate of Solution
4. Temperature
For liquids and solids, increase
 temp., increase the rate
For gases, increase the temp.,
 decrease the rate
           Dilutions
M1 x V1 = M2 x V2


Volume may be any units as
 long as you are consistant
        Dilutions

Method used to dilute
 solutions to other
 concentrations
         Dilutions
Sample problem # 1
Given 2.00 L of a 2.50 M
 NaOH solution, what
 would the molarity be if
 the solution were diluted
 to a volume of 5.00 L?

				
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posted:9/22/2012
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