Video Transcript
Which of the following is not a
property of ethene? (A) Liquid at room temperature. (B) Flammable. (C) Volatile. (D) Colorless. Or (E) soluble in nonpolar
solvents.
This question asks us which of the
listed properties does not describe ethene. Ethene is an alkene. An alkene is a hydrocarbon with at
least one carbon-to-carbon double bond. Ethene has this structural formula,
with only two carbons. Ethene is a small hydrocarbon. Hydrocarbon chain length impacts
the properties of the molecules. Keeping in mind that ethene is a
small hydrocarbon, let’s have a look at some properties that are impacted by
hydrocarbon length.
As hydrocarbons get longer, the
strength of the dispersion forces between them increases. The diagram represents the
dispersion forces between ethene molecules. Dispersion forces are the
electrostatic interactions between temporary dipoles of molecules. So, ethene has weaker dispersion
forces compared to longer hydrocarbons. This makes ethene very volatile,
since volatility is inversely related to the strength of the dispersion forces
between molecules in a substance.
Ethene is also very flammable,
since it is easier to ignite a short chain of carbons compared to a longer
hydrocarbon chain. Hydrocarbons are also often
colorless and nonpolar, and ethene has both of these properties. This makes ethene soluble in
nonpolar solvents, and so answer choices (B), (C), (D), and (E) are all incorrect
since these properties describe ethene. This leaves answer choice (A),
liquid at room temperature.
As we saw, ethene is very volatile,
and volatility means a substance evaporates readily at room temperature and normal
pressures. In fact, ethene has a very low
boiling point of approximately negative 104 degrees Celsius. So at room temperature, ethene
exists as a gas. Being a very volatile compound with
a very low boiling point, at normal pressure and room temperature, ethene is not a
liquid but a gas.
So, which of the following is not a
property of ethene? Answer choice (A) liquid at room
temperature.
