Video Transcript
Which of the following is not a
common use of alkanes? (A) Solvents, (B) gas burners, (C)
plastics, (D) propellants, (E) fuels.
In this question, we need to
identify which answer choice is not a typical use of alkanes. Alkanes are saturated hydrocarbons
with only single bonds between carbon atoms. Methane is the simplest alkane and
is the major component of natural gas. We are probably familiar with
burning natural gas in the laboratory with a Bunsen burner. But the alkanes in natural gas are
used around the world as fuel because they undergo combustion reactions with oxygen
and release energy. This energy can be used to heat
homes or cook food. Pentane is another example of an
alkane that is used for fuel, as it is a component of gasoline. We can apply this information to
determine that answer choices (B) and (E) are incorrect, since they are common uses
of alkanes.
Now let’s consider answer choices
(A) and (D). Alkanes that are liquids at room
temperature, such as hexane and heptane, make good solvents of other organic
molecules. This is because alkanes are
nonpolar molecules. There is a very small difference in
electronegativity between carbon and hydrogen atoms. Therefore, all the bonds in the
molecule are nonpolar. As a result, these liquid alkanes
make good nonpolar solvents and can easily dissolve other nonpolar molecules. Alkanes, such as propane and
butane, which are gases at room temperature, are often used as propellants in
aerosol and foam products. For example, these propellants are
often found in products such as hairspray and shaving cream. Knowing these common uses of
alkanes allows us to eliminate answer choices (A) and (D).
This leaves only answer choice
(C). Some common plastics are made from
alkenes. Alkenes are unsaturated
hydrocarbons that contain at least one carbon–carbon double bond. Ethene is an example of an alkene
used to make a plastic polymer. In the presence of a catalyst,
other chemicals, heat, and pressure, the polymer polyethylene or polyethene can be
formed from ethene monomers. This specific plastic is used to
make plastic bags and plastic bottles.
So, which of the following is not a
common use of alkanes? The answer is plastics, or answer
choice (C).
