carbon dioxide’s pressure is therefore × 1,200
torr. (D) is correct.
Drill 2
- E Think back to the first phase change diagram. As heat was removed
from the system, the substance moved from gas phase to liquid phase to
solid phase. Which process is clearly doing that here? In choice (E), a gas is
condensing into a liquid, so (E) is the correct answer.
- B Remember that sublimation is the direct conversion of a solid into a
gas, so (B) is correct.
- E A decrease in entropy means an increase in order. There is an
increase in order (and restriction in molecular motion) as a gas condenses to
a liquid. Choice (E) is correct.
- D Heat of fusion is associated with the process of melting or freezing.
Do any choices involve one of these? Yes; in choice (D), solid bromine
melts. If this change took place solely at the melting point, then the heat of
fusion of bromine would equal the enthalpy change for the process. Choice
(D) is the correct answer.
- T, F You know what to do with this question type by now. Is statement I
true or false? It’s true. What about statement II? It’s false. Hydrogen
bonds are stronger than most intermolecular forces but far weaker
than covalent or ionic bonds.
- F, F As you go up into higher elevations, the atmosphere exerts less
pressure. As the pressure over a substance decreases, the boiling point
of the substance will also decrease. Since water boils at 100°C at sea-
level (1 atm), it will boil below 100°C at higher elevations. So
statement I is false. Statement II is also false. Average kinetic energy
is a measure of temperature, not pressure. So even if the pressure on a
sample increases, if its temperature remains constant, so will its
