Lab 6-1
Catherine Puga
1. Paradichlorobenzene has a very strong odor while potassium iodide does
not. PDCB(paradichlorobenzene) is more volatile then potassium iodide.
Volatile means that the molecular substance can evaporate easily and when
it evaporates, it lets off a strong smell. A substances ability to evaporate
depends on the strength of its bonds. Potassium iodide had ionic bonds
whereas PDCB has London Dispersion Forces. LDF’s are the weakest type of
intermolecular bonds; therefore, PDCB evaporates easier so it has a stronger
odor.
2. The statement “The lower melting point of paradichlorobenzene is evidence
that covalent bonds are weaker than ionic bonds” is false.
Paradichlorobenzene does have a lower melting point, however this is
because PDCB has a non-polar bond so it has London Forces for
intermolecular bond, which are weaker than ionic bonds. It has a covalent
intramolecular bond but intramolecular forces do not affect melting point,
only intermolecular forces do.
3. Potassium Iodide conducts electricity in its liquid state at 75 watts but not in
its solid state. For a substance have electrical conductivity, there needs to be
space for the electrons to move and electrons that are capable of moving.
Potassium iodide is a salt. Salts do not conduct electricity well in their solid
states because there is no empty space in its ionic structure. However, when
melted, the ions break apart, allowing the electrons to move.
4. A sample of paradichlorobenzene has non-polar covalent intermolecular
forces and its intermolecular forces are London Dispersion Forces.
5. The gray cells are substances that have not been tested in ethanol. Ethanol is
mostly non-polar but it has some polar properties due to the OH part of it so
that iodine, a non-polar substance, can dissolve in it as well as potassium
iodide, a polar substance. I would predict that ethanol would dissolve 1 and
3 because both PDCB and Naphthalene are both non-polar. I would also
predict that KI, Wood’s Metal and graphite are all slightly soluble; they
would not dissolve completely but they would dissolve some because of the
polar properties of ethanol.
6. The statement “like dissolves like” means that polar solutes will dissolve
polar substances and non-polar solutes will dissolve non-polar substances.
Water is a polar solute and it dissolved sucrose and potassium iodide, both
polar substances. Cyclohexane is a non-polar solute and it dissolved PDCB,
Iodine, and Naphthalene, all of which are non-polar substances. However, if
the intermolecular bonds are strong enough, some substances will not
dissolve in either solute. Wood’s metal, which has metallic bonds, is a good
example.