# Solutions

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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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 views: 137 posted: 9/22/2012 language: English pages: 70