Solutions

Describes the types of solutions, solubility, miscibility

1. 1
Solutions

2. 2
Solute
Solvent
Solution

3. 3
How much I have to add to have a GOOD
lemonade?
Is it
concentrated?
Is it diluted?
How would you prepare a lemonade?

4. 4
Definitions
Solution
Homogeneous mixture where particles are
uniformly distributed throughout.
Solute
The substance that dissolves in a solvent
Solvent
The substance in which a solute dissolved

5. 5
Solutions
When water is a solvent, the solution is
aqueous.
Solvents may be gases: air is a
solution of nitrogen, oxygen, argon, and
other gases.
Steel is an alloy, solution of one solid
dissolved in another solid are solutions
of various metals.

6. 6
Solubility
The maximum amount of solute that
dissolves in a fixed quantity of a particular
solvent.
Soluble
Capable of being dissolved.
Salt is soluble in water

7. 7
Solubility Terms
Miscible
Two liquids that are soluble in each other.
If they are soluble in any proportion, they
are said to be completely miscible.
Liquids that are partially soluble are said to
be partially miscible
Immiscible
Liquids that are not soluble when mixed.

8. 8
Solubility Terms
Insoluble. When a substance does not
appear to dissolve in a solvent.
A concentrated solution has a
relatively large amount of solute for
given quantity of solution.
A dilute solution has a smaller amount
of solute for a given quantity of solution.

9. 9
Insert figure 14.4
Oil is Not Soluble in Water

10. 10
Ionic Solubility
Water will dissolve many ionic
compounds (salts).
When salts dissolve in water:
1. The ionic forces holding ions together are
broken.
2. The attractive forces holding some of the
water molecules together are broken.
3. Ions must interact with the solvent
molecules to form attractive forces.

11. 11
Ionic Solubility
The process in which water molecules
surround the ions is called hydration.
For other solute/solvent interactions, this
process is called solvation.

12. 12
Insert figure 14.3
Dissolving an Ionic Compound in Water

13. 13
Solubility of Covalent Compounds
Like dissolves like.
Non-polar solutes dissolve in non-polar
solvents (like oil, thinner, soaps).
Polar solutes dissolve in polar solvents
(water, alcohol, acids).
Hydrogen bonding between solute and
solvent molecules plays an important role.

14. 14
Solubility Equilibria
Most solutes have a limited solubility in a given
solvent.
When more solute is present than the solubility
limit, a dynamic equilibrium is established:
solute + solvent solution
A solution of this type is said to be saturated.
 A solution that contains less solute than the solubility
limit is unsaturated.
dissolving
crystallizing

15. 15
Effects of Temperature on Solubility
Most solids become more soluble as
temperature increases. (There are some
exceptions.)
If a saturated solution is cooled, with solid present,
more solid will precipitate until equilibrium is re-
established.
If a saturated solution is cooled with no solid
present, sometimes precipitation does not occur
immediately. The solution is said to be
supersaturated.

16. 16
Concentration
The concentration of a solution is the
amount of solute dissolved in a certain
quantity of solvent.
One measure of concentration is molarity M.
M = (# mol solute)/1 Liter of solution

17. 17
Molarity Problem
Tell how to prepare 250 mL of a 3.00 M solution of NaCl.
M= # moles / Liters
1. Convert mL to L:
1L → 1000 mL
x → 250 mL
2. Convert grams to mol with Molar Mass
Na 23.0 + Cl 35.45 = 58.45 g/mol
58.45 g → 1 mole
x → 3 moles (3M)
3. Convert grams to volume
175.35 g → 1 L
x → 0.250 L|
g.
mole
g.mole
35175
1
45583


L
mL
LmL
250.0
1000
1250


g
L
gL
84.43
1
35.175250.0



18. 18
Preparing solutions of a given
molarity
The plan for solving the above problem was:
mL
L moles grams
To actually prepare the solution, 250 mL of 3.00 M NaCl:
1. Transfer 43.8 g of NaCl to a 250 mL volumetric flask
partly filled with distilled water.
2. Shake to dissolve.
3. Add enough water to the flask to reach the mark
4. Stopper the flask and invert several times to mix
thoroughly.

19. 19
Another Molarity Problem
How many mL of 12.00 M HCl solution
are required to deliver 0.500 mol?
L = moles/M = (0.500 mol)/(12.00 mol/L)
=0.0417 L
0.0417L x 1000 mL/L= 41.7 mL

20. 20
Percent by Volume [%(v/v)]
Percent by Volume =
[(volume solute)/(volume solution)]x100%
Calculate the percent by volume alcohol
prepared by mixing 15.0 mL with enough
water to make a total volume of 50.0 mL.
Percent by volume =
[(15 mL)/(50 mL)] x 100 = 30%(v/v)
50 mL → 100%
15 mL → x
%30
50
%10015


mL
mL

21. 21
Percent by mass [%(w/w)]
Percent by mass
= [(mass solute)/(total mass of solution)]x100%
=[(g solute)/(g solute + g solvent)] x 100%
How many g of NaCl are required to prepare
100 g of a 5.0% solution?
Mass solute = (percent/100)x(total mass)
= (5/100)x100 g = 5.0 g NaCl
100g →100%
x → 5%
g
g
5
%100
100%5



22. 22
Preparation of Solutions by Dilution
Calculate the volume of 10.0%(v/v) ethanol
require to prepare 500 mL of 5.00% ethanol.
V
1
C
1
= V
2
C
2
Desired [ ]
C
1
= 10.0, V
2
= 500 mL, C
2
= 5.00
V
1
= V
2
C
2
/C
1
= (500mL)(5.00%)/(10.0%)
= 250 mL
mL
mL
C
CV
250
%10
%5500
2
11




23. 23
Colligative Properties
Properties of liquids change when solutes are
dissolved in them:
boiling point is raised
melting point is decreased
The higher the concentration of solute particles, the
greater the effect.
Colligative Properties are properties of
solutions that depend on the number of
dissolved solute particles.

24. 24
Counting Particles
A solution of 1.00 L of a 1.00 M solution
of glucose contains 6.022 x 10
23
particles
of glucose molecules.
But a solution of 1.00 L of a 1.00 M
solution of NaCl contains 2x6.022x10
23
particles because of ionization.
The freezing point depression of 1.0 M
NaCl is almost twice that of 1.0 M
glucose.

25. 25
Colloids
The temporary dispersion of one substance in
another is a mixture called a suspension.
Part of the mixture will settle out from the
other part or can be separated by filtration.
Colloids or colloidal dispersions are defined
as mixtures having a particle size of 1.0 nm -
100 nm.
Colloids appear milky or cloudy. They scatter
light by the Tyndall effect.

26. 26
Colloids
There are 8 different types of colloids
based on the particles and the phase of
the dispersal agent.
Some examples are foams and
emulsions.
Colloids are stabilized by emulsifying
agents such as soap or bile salts.

27. 27
Osmosis and Dialysis
Certain materials are:
Permeable: allow water and solvents to pass through.
Impermeable: do not allow solvents to pass.
Semipermeable: material which allows solvent molecules to
pass, but not solute molecules.
The process of solute molecules passing through a
semipermeable membrane is called osmosis.
If small ions and molecules pass through the
membrane with the solvent, but colloidal particles are
retained the process is called dialysis.

28. 28
Insert figure 14.16
A Semipermeable Membrane

29. 29
Osmosis
The pressure required to prevent the flow of
solvent from the less concentrated side to the
more concentrated side of a membrane is
called the osmotic pressure.
Isotonic solutions is one that has the same
osmotic pressure as the fluid in a living cell.
Hypotonic solutions have a lower
concentration than inside the cell. Water
flows from a solution into a cell.

30. 30
Osmosis in Cells
The rupture of a cell by hypotonic
solutions is called plasmolysis (or
hemolysis in the case of red blood
cells)
Hypertonic solutions contain a greater
concentration of particles than the fluid
in cells. Water will flow from the cells to
the solution.
This process is called crenation.