Video Transcript
Which of the following alkenes is
the least volatile? (A) Ethene, (B) propene, (C)
butene, (D) pentene, or (E) hexene.
In this question, we need to
identify the alkene that is the least volatile. An alkene is an unsaturated
hydrocarbon with at least one carbon-to-carbon double bond. When a substance such as an alkene
is described as volatile, it readily evaporates at normal pressures and
temperatures. The volatility of a substance is
inversely related to its size. When an alkene is very small and
has weak intermolecular forces, it is more volatile.
We are given five names of
different substances in the answer choices. We can see that all five of these
compounds are alkenes because their names end in -ene. The prefixes of these names can
help us determine the structure and size of these alkenes. The prefix in an alkene’s name
tells us the number of carbon atoms in the longest hydrocarbon chain. We can see that answer choice (E),
hexene, has six carbons. This is the longest alkene given in
the answer choices. Hexene would be the least volatile
since it is the largest hydrocarbon of the five and would have the strongest
intermolecular forces between its molecules.
So, answer choice (E) is
correct. The alkene that would be the least
volatile of the given alkenes is answer choice (E) hexene.
