1. CHAPTER 8 Solutions General, Organic, & Biological Chemistry
Janice Gorzynski Smith

2. CHAPTER 8: Solutions Learning Objectives:
Define solutions: possible states, solvent vs solute
Solubility: saturated vs unsaturated, effects of temperature & pressure
Electrolytes vs non-electrolytes
Concentration: %w/v, %v/v, ppm, Molarity
Dilution calculations
Colligative Properties:
Boiling point elevation
Freezing point depression
Osmotic pressure
Smith. General Organic & Biolocial Chemistry 2nd Ed.

3. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Mixtures
Solutions
A heterogeneous mixture does not have a uniform composition throughout the sample.
Salad dressing is a heterogeneous mixture.
A homogeneous mixture has a uniform composition throughout the sample.
Solutions are homogeneous mixtures.
Solutions consist of two parts:
The solute is the substance present in a lesser amount.
Use modeling kit!
The solvent is the substance present in a larger amount.
An aqueous solution has water as the solvent.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

4. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
2 Types of Solutions
Three different types of solutions:
a solution of
gases (O2, CO2,
and N2)
Use modeling kit!
an aqueous
solution of NaCl
(a solid in a liquid)
Hg(l) dissolved
in Ag(s)
(a liquid in a
solid)
Smith. General Organic & Biolocial Chemistry 2nd Ed.

5. A substance that conducts an electric current in water
Solutions
Electrolytes
A substance that conducts
an electric current in water
is called an electrolyte.
A substance that does
not conduct an electric
current in water is
called a nonelectrolyte.
Use modeling kit!
NaCl(aq) dissociates into
Na+(aq) and Cl−(aq)
H2O2 does not
dissociate
Smith. General Organic & Biolocial Chemistry 2nd Ed.

6. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Solubility
Solubility is the amount of solute that dissolves in a given amount of solvent.
A saturated solution contains the maximum
number of grams of solute that can dissolve.
An unsaturated solution contains less than the
maximum number of grams of solute that can dissolve.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

7. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Solubility
Solubility can be summed up as “like dissolves like.”
Most ionic and polar covalent compounds are soluble in water, a polar solvent.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

8. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Solubility
Small neutral molecules with O or N atoms that can hydrogen bond to water are water soluble.
Use modeling kit!
Example: ethanol can hydrogen bond to water.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

9. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Solubility
Nonpolar compounds are soluble in nonpolar
solvents (i.e., like dissolves like).
Octane (C8H18) dissolves in CCl4 because both are
nonpolar liquids that exhibit only London dispersion
forces.
Use modeling kit!
octane
CCl4
octane + CCl4
Smith. General Organic & Biolocial Chemistry 2nd Ed.

10. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Effects of Temperature & Pressure
For most ionic and molecular solids, solubility generally increases as temperature increases.
By dissolving a solid in a solvent at high
temperature and allowing it to cool slowly, a
supersaturated solution can be made.
A supersaturated solution contains more than
the predicted maximum amount of solute at a
given temperature.
Use modeling kit!
In contrast, the solubility of a gas decreases with increasing temperature.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

11. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Effects of Temperature & Pressure
Henry’s law: The solubility of a gas in a liquid is proportional to the partial pressure of the gas above the liquid.
The higher the pressure, the higher the solubility
of a gas in a solvent.
Use modeling kit!
closed can of soda
higher CO2 pressure
higher CO2 solubility
open can of soda
lower CO2 pressure
lower CO2 solubility
Smith. General Organic & Biolocial Chemistry 2nd Ed.

12. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Concentration: w/v %
Weight/volume percent concentration, (w/v)%, is the number of grams of solute dissolved in 100 mL of solution.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

13. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Concentration: v/v %
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

14. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Concentration: ppm
When a solution contains a very small concentration
of solute, it is often expressed in parts per million.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

15. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Concentration: Molarity
Molarity is the number of moles of solute per liter of
solution, abbreviated as M.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

16. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Dilution
Dilution is the addition of solvent to decrease the
concentration of solute. The solution volume changes,
but the amount of solute is constant.
Use modeling kit!
M1V = M2V2
initial values
final values
Smith. General Organic & Biolocial Chemistry 2nd Ed.

17. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties
Colligative properties are properties of a solution
that depend on the concentration of the solute but
not its identity.
Thus, the number of dissolved solute particles affects the properties of the solution, but the identity of the solute does not.
Use modeling kit!
Colligative properties include the elevation of the boiling point, the lowering of the melting point, and the pressure due to osmosis.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

18. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Boiling Point Elevation
A volatile solute readily escapes into the vapor phase while a nonviolatile solute does not .
Boiling point elevation: A liquid solution that
contains a nonvolatile solute has a higher boiling
point than the solvent alone.
The amount that the boiling point increases depends only on the number of dissolved particles.
Use modeling kit!
One mole of any nonvolatile solute raises the
boiling point of 1 kg of H2O the same amount,
0.51 oC.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

19. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties:
Freezing Point Depression
Freezing point depression: A liquid solution that
contains a nonvolatile solute has a lower freezing
point than the solvent alone.
The amount of freezing point depression depends
only on the number of dissolved particles.
Use modeling kit!
One mole of any nonvolatile solute lowers the
freezing point of 1 kg of H2O by the same amount,
1.86 oC.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

20. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Osmosis
The membrane that surrounds living cells is a
semipermeable membrane.
Semipermeable membranes allow water and small
molecules to pass across, but ions and large molecules cannot.
Osmosis is the passage of water and small
molecules across a semipermeable membrane from
a solution of low solute concentration to a solution
of higher solute concentration.
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

21. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Osmosis
Use modeling kit!
Osmotic pressure is the pressure that prevents
the flow of additional solvent into a solution on
one side of a semipermeable membrane.
Smith. General Organic & Biolocial Chemistry 2nd Ed.

22. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Osmosis
Use modeling kit!
Smith. General Organic & Biolocial Chemistry 2nd Ed.

23. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Osmosis
isotonic
solution
hypotonic
solution
hypertonic
solution
Same osmotic pressure as the body:
Use modeling kit!
Lower osmotic pressure as the body:
Higher osmotic pressure as the body:
0.92% (w/v) NaCl
Water diffuses into the cell
Water diffuses out of the cell
5.0% (w/v) glucose
Smith. General Organic & Biolocial Chemistry 2nd Ed.

24. Smith. General Organic & Biolocial Chemistry 2nd Ed.
Solutions
Colligative Properties: Osmosis
hemodialysis
In the human body, blood is filtered through the kidneys by the process of dialysis.
Use modeling kit!
In dialysis, water, small molecules, and ions can pass through the semipermeable (dialyzing) membrane; only large biological molecules like proteins and starch molecules cannot.
This allows waste products like urea to be removed from the bloodstream and eliminated in the urine.
Smith. General Organic & Biolocial Chemistry 2nd Ed.