Video Transcript
Which of the following statements
describes bromine dissolving in hexane? (A) A nonpolar substance dissolving
in a polar solvent. (B) A polar substance dissolving in
a nonpolar solvent. (C) A polar substance dissolving in
a polar solvent. (D) A nonpolar substance dissolving
in a nonpolar solvent.
First, let’s define the terms polar
and nonpolar. A polar molecule will have a
nonuniform electron density. This means that some portions of
the molecule will have a partial negative charge and some portions of the molecule
will have a partial positive charge. Nonpolar molecules will have a
uniform electron density. This is the case when the electrons
are equally shared in all of the bonds in the molecule or when the polar bonds in
the molecule are symmetrically distributed. Bromine is a diatomic molecule
consisting of two single-bonded bromine atoms. As the atoms are the same, they
will have the same electronegativity. This means that the electrons in
the bond will be equally shared between the two bromine atoms. Thus, the molecule of bromine is
nonpolar.
As bromine is the substance being
dissolved, we can eliminate answer choices (B) and (C). Hexane, chemical formula C6H14,
only contains carbon and hydrogen atoms. The electronegativity of a carbon
atom is approximately equal to the electronegativity of a hydrogen atom. Because the electronegativity
values are so similar, we can consider the electrons in a carbon–hydrogen bond to be
equally shared. As a molecule of hexane only
contains nonpolar carbon–carbon and carbon–hydrogen bonds, hexane will be
nonpolar. Therefore, the statement that
describes bromine dissolving in hexane is answer choice (D), a nonpolar substance
dissolving in a nonpolar solvent.
