multiple of five, depending on the other compounds. There are six chlorines on the right, so
you must place a “3” before the Cl 2 on the left. The equation is now fully balanced and it’s
clear that the answer is indeed five, choice C.66 . C
Specific gravity = density of substance/density of water
67 . C
Ideal gases can be described by the kinetic molecular theory of gas. One part of this model is
that collisions are elastic; there is no overall net gain or loss of energy. Inelastic collisions do
occur in real gases. Also, a nuclear fusion reaction is a reaction in which two nuclei collide to
form a new, heavier nucleus.68 . B
A Lewis base is a compound that can donate an electron pair. Choice B, hydrazine, consists of
two nitrogens bonded to each other and to two hydrogen atoms each. A nitrogen atom has a
valence of five, and when it’s bonded to another nitrogen and two hydrogens, it’s using only
three of its five valence electrons. Therefore, each nitrogen will have a pair of unbonded
electrons. This makes hydrazine able to act as an electron pair donor, or Lewis base.
69 . C
You know from the Pauli exclusion principle that no two electrons in the same atom can have
the identical quantum number. So, with n, l, and ml the same, you may be tempted to say the
two electrons must be in different atoms. However, there is a fourth quantum number that
could be different. The n value indicates that these electrons are in the same shell. The value
of n also limits the value of l, defining the possible subshells the electrons can occupy. If they
have the same l value, they must be in the same subshell if they are in the same atom. Well,
the l value limits the ml value, which defines the specific spatial orientation of the orbital the
electrons are in. If the ml value is the same for two electrons, they are in the same orbital. So,
the identical ml value puts these two electrons in the same orbital. You know that the last