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easy chem lab. Do not copy anything off the internet. Do it all on your own
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SOLUTIONS
INTRODUCTION
A solution is a homogeneous mixture of two or more substances. The substance that is present
in the larger amount is known as the solvent. The substance that is present in the smaller amount
is known as the solute. The solute is dissolved into the solvent. Most solutions with which we
are familiar are liquids. However, solids, liquids or gases may be either solute or solvent. For
example, air is a solution of oxygen and other gases in nitrogen. Oxygen is the solute and nitrogen
is the solvent.
The solubility of a substance depends on:
1. The nature of the solute and solvent
2. The amount of solute and solvent
3. The temperature
4. The pressure (for gaseous solutions).
A solution will form between the solute and solvent when the attractive forces between the
solute and solvent are large enough to overcome the attractive forces within the solute and
within the solvent. Therefore, a polar solute will dissolve in a polar solvent and a non-polar
solute will dissolve in a non-polar solvent. For this reason we say that “like dissolves like.” For
aqueous solutions temperature plays a role in the amount of solute which will dissolve. Usually,
the higher the temperature, the more solute will dissolve.
PROCEDURE
(Professor Demonstration)
A. Paper discs.
A jar is filled with two liquids, water and carbon tetrachloride. Some paper discs with graphite
on one side are added to the jar. Observe the orientation of the discs in the jar. Shake the jar
and observe the orientation of the disks after the contents have settled.
Questions:
1. What is the polarity of the two liquids in the jar? What does that tell you about the polarity
of the fibers in the paper? About the polarity of graphite?
2. Carbon tetrachloride is denser than water so it is on the bottom. Cyclohexane is less dense
than water and has the same polarity as carbon tetrachloride. What would be the orientation
of the disks, if cyclohexane replaced carbon tetrachloride in the jar?
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B. Three Layers
A large test tube is filled with cyclohexane, water, and carbon tetrachloride. They form three
layers with the cyclohexane on the top and the carbon tetrachloride on the bottom. A small
amount of iodine is added.
Questions:
1. What happens to the appearance of the layers in the test tube after the iodine is added?
What does this tell you about the polarity of iodine?
2. What would happen to the appearance of the contents of the test tube if it were stoppered
and the contents mixed? (Remember “like dissolves like.”)
Questions:
1. NaCl is soluble in water but I2 is not. Explain. What type(s) of intermolecular forces are
involved?
2. Would you expect sugar to dissolve in gasoline? Explain. What type(s) of intermolecular
forces are involved?
Sugar
Gasoline
CH2
3. Would
you
expect
carbon
O
CH
HO
CH
CH
HO
OH
CH
HC
H3C
H2C
CH2
CH2
OH
CH2
OH
monoxide to be soluble in water? Why or why not?
4. Does carbon tetrahydride (methane) dissolve in water? Explain.
CH2
CH3
CH2
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