presentation of solution of chemistry ppt

1. Solutions

2. Solution Chemistry
Properties of Solutions
Types of Solutions
Concentrations of Solutions
Colligative Properties of Solutions

3. Parts of a solution
 A solution is a
HOMOGENEOUS
mixture of 2 or more
substances in a single
phase.
 One constituent is
usually regarded as the
SOLVENT and the
others as SOLUTES.

4. Solute + Solvent = Solution
 SOLUTE – the part of a
solution that is being
dissolved (usually the
lesser amount)
 SOLVENT – the part of
a solution that dissolves
the solute (usually the
greater amount)
Solute Solvent Example
solid solid Alloys (brass, steel)
solid liquid Salt water
gas solid Air bubbles in ice
cubes
liquid liquid mixed drinks
gas liquid Soft drinks
gas gas Air

5. Terms
 Liquids that are soluble in each other
are said to be miscible
 Liquids that are insoluble in each
other are immiscible
 Remember “like dissolves like.”
 Polar substances dissolve in polar
substances
 Nonpolar substances dissolve in
nonpolar substances

6. Types of Solutions
 Solutions can be classified as
saturated or unsaturated.
 A saturated solution contains the
maximum quantity of solute that
dissolves at that temperature.
 An unsaturated solution contains less
than the maximum amount of solute
that can dissolve at a particular
temperature

7. Supersaturated Solutions
 Contain more solute than is
possible to be dissolved
 Supersaturated solutions are
unstable. The supersaturation is
only temporary, and usually
accomplished in one of two
ways:
• Warm the solvent so that it will
dissolve more, then cool the
solution
• Evaporate some of the solvent
carefully so that the solute does
not solidify and come out of
solution.

8. Practical Application
 Supersaturated
solution of
sodium acetate
to make a “heat
pack.”

9. Ionic Solutions
 How do we know ions
are present in aqueous
solutions?
 The solutions conduct
electricity!
 They are called
ELECTROLYTES
 HCl, MgCl2, and NaCl
are strong electrolytes.
They dissociate
completely (or nearly
so) into ions.

10. Nonelectrolytes
 Substances that
dissolve in water but
do not conduct
electricity:
 Sugar
 Ethanol
 Ethylene Glycol

11. Electrolytes in the Body
 Carry messages to and
from the brain as
electrical signals
 Maintain cellular function
with the correct
concentrations
electrolytes

12. Solubility
 Factors affecting solubility:
 Temperature – In general, solubility
increases with temperature
 Pressure - The higher the pressure
above a liquid, the more soluble the gas
is in the liquid.

13. Temperature and Solubility

14. Pressure and Solubility

15. Concentration of Solutions
 The amount of solute in a solution is given by its
concentration.
Molarity(M) = moles solute
liters of solution

16. Learning Check
 How many grams of NaOH
are required to prepare 400.
mL of 3.0 M NaOH
solution?
 47 g

17.  An IDEAL SOLUTION is
one where the properties
depend only on the
concentration of solute.
 Need concentration units to
tell us the number of solute
particles per solvent particle.
 The unit Molarity does not do
this
Concentration Units

18. Other concentration units:
 Molality (m)
 % by mass =
m of solution =
mol solute
kilograms solvent
grams solute
grams solution

19. Colligative Properties
 On adding a solute to a solvent, the properties
of the solvent are modified.
 Vapor pressure  decreases
 Freezing point  decreases
 Boiling point  increases
 Osmosis is possible (osmotic pressure)
 These changes are called COLLIGATIVE
PROPERTIES.
 They depend only on the NUMBER of solute
particles relative to solvent particles, not on
the KIND of solute particles.

20. Vapor Pressure
•If we add a solute to a liquid, the
amount of surface area available
for the escaping solvent
molecules is reduced because
some of that area is occupied by
solute particles. Therefore, the
solvent molecules will have a
lower probability to escape the
solution than the pure solvent.
That fact is reflected in the lower
vapor pressure for a solution
relative to the pure solvent.

21. Freezing Point Depression
 When water freezes, the
molecules take on an
orderly pattern. The
presence of a solute in
water disrupts the
formation of this pattern.
More kinetic energy
(temperature) must be
withdrawn for the water to
solidify, thus lowering the
temperature at which it
will freeze.

22. Boiling Point Elevation
 Since a substance boils when the vapor
pressure of the liquid equals the
atmospheric pressure, and adding a
solute decreases vapor pressure, the
boiling point of the solution will be higher
than the pure solvent.

23. Osmosis in cells: Through a cell membrane, water flows
towards the more concentrated solution.

24. A little solution humor…
 What do you call a tooth in a glass of
water?
 A one “molar” solution!