41 . E
The first ionization energy is the energy required to completely remove an electron from an
atom or ion. The closer and more tightly bound an electron, the higher the ionization energy
will be. The atomic radius decreases across a period with increasing atomic number due to the
increase in the effective nuclear charge. So boron would be the largest atom that would be the
easiest and require the least energy to remove an electron.42 . E
The absolute temperature of a sample of gas is directly proportional to the average kinetic
energy of the particles, independent of their identity or other factors. If the samples are at the
same temperature, then by the definition of temperature they have the same average kinetic
energy.
43 . C
This is the definition of normal boiling point; it’s the boiling point of a substance at sea level,
where atmospheric pressure is 1 atm. A and C describe the boiling point, but not specifically
normal boiling point. D is the value of the normal boiling point of water (the problem doesn’t
specify what liquid).
44 . E
A beta particle has mass number 0 and charge −1, the same as an electron. Beta decay means
the nucleus is giving off a beta particle as a product. The balanced nuclear equation is:
(^2411) Na → (^0) − 1 e + (^2412) Mg
Note that you don’t need to know the half-life—it’s a distracter.
45 . D
In the Lewis structure for SO 2 , there is a lone pair of electrons on S, giving a bent structure and
a polar molecule. The structures of the other four species are symmetrical, and the species are
all nonpolar.
46 . C
The molecular structure of NH 3 is a triangular pyramid. H 3 O+ is isoelectronic with NH 3 and has
the same shape. BH 3 has no lone pair on the central atom and is a triangular-planar molecule;