Answers and Explanations
REVIEW QUESTIONS
1 . E
Boyle’s law states that when a gas is held at constant temperature, its pressure and volume are
inversely proportional. This means that as the pressure increases, the volume decreases, and
vice versa. Of the answer choices, the only one that involves both pressure and volume—in
addition to a controlled variation of one of the variables—is choice E. When a balloon is placed
in a bell jar, the volume of the balloon will increase as a vacuum is being drawn in the jar.
Boyle’s law can be used to predict this behavior.
2 . C
This question is an application of Charles’s law, which states that at constant pressure, the
volume and temperature of a gas will vary in direct proportion to each other. If a 50 L volume
of gas is heated from standard temperature, which is 273 K, to two times standard
temperature, 576 K, the volume will double as well. Therefore, the volume of the gas will
increase from 50 L to 100 L.
3 . 74
Using the ideal gas law, we can determine the number of moles of the gas:
The molecular weight, or molar mass, of the gas can then be found by dividing the mass of the
gas by the number of moles it contains: 2.5 g/0.034 mol = 74 g/mol.
4 . The conditions that define an ideal gas are low pressure and high temperature. Under these
conditions, the ideal gas assumption that gas molecules have no intermolecular forces and
occupy no volume is most valid.