Unit 3: Gases

21. The volume occupied by one mole of an ideal gas at STP is approximately:

a) 22.4 L
b) 24.0 L
c) 18.0 L
d) 30.0 L
Answer: a) 22.4 L

22. Graham’s law of effusion relates the rate of effusion of a gas to:

a) Its molar mass
b) Its temperature
c) Its volume
d) Its pressure
Answer: a) Its molar mass

23. In which of the following conditions does a real gas behave most like an ideal gas?

a) High pressure and low temperature
b) Low pressure and high temperature
c) High pressure and high temperature
d) Low pressure and low temperature
Answer: b) Low pressure and high temperature

24. The term “effusion” refers to:

a) The process of a gas escaping through a small hole into a vacuum
b) The process of a gas dissolving in a liquid
c) The mixing of gases
d) The increase in volume of a gas with temperature
Answer: a) The process of a gas escaping through a small hole into a vacuum

25. Which of the following gases would have the highest rate of effusion under identical conditions?

a) Oxygen (O₂)
b) Nitrogen (N₂)
c) Carbon dioxide (CO₂)
d) Hydrogen (H₂)
Answer: d) Hydrogen (H₂)

26. The concept of “partial pressure” is used to describe:

a) The pressure of an individual gas in a mixture
b) The total pressure of a gas mixture
c) The pressure of the solvent in a solution
d) The pressure of the gas at STP
Answer: a) The pressure of an individual gas in a mixture

27. The root-mean-square speed of gas molecules is proportional to:

a) The square root of the gas’s molar mass
b) The square root of the temperature
c) The gas’s density
d) The volume of the gas
Answer: b) The square root of the temperature

28. The real gas equation that accounts for the volume occupied by gas molecules and intermolecular forces is:

a) Ideal gas law
b) Van der Waals equation
c) Dalton’s law
d) Graham’s law
Answer: b) Van der Waals equation

29. The term “compressibility” refers to:

a) The ability of a gas to expand
b) The ability of a gas to decrease in volume under pressure
c) The ability of a gas to dissolve in liquids
d) The ability of a gas to mix with other gases
Answer: b) The ability of a gas to decrease in volume under pressure

30. The kinetic molecular theory explains the behavior of gases in terms of:

a) Molecular collisions and intermolecular forces
b) The constant motion of gas molecules and the absence of intermolecular forces
c) The solubility of gases in liquids
d) The increase in gas volume with temperature
Answer: b) The constant motion of gas molecules and the absence of intermolecular forces