Name:    Chapter 10  Online Practice

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.  You may use a calculator to complete these problems.

1.

At constant temperature, 14.0 L of O2 at 0.882 atm is compressed to 1.75 L. What is the final pressure of O2?
 a. 0.111 atm b. 0.142 atm c. 7.06 atm d. 21.6 atm e. 27.8 atm

2.

If the volume of a confined gas is quadrupled while its temperature remains constant, what change will be observed?
 a. The pressure of the gas will decrease to 1/4 its original value. b. The pressure of the gas will quadruple. c. The density of the gas will decrease to 1/2 its original value. d. The average velocity of the molecules will quadruple. e. The average velocity of the molecules will double.

3.

A balloon is filled with He gas to a volume of 3.22 L at 32 °C. The balloon is placed in liquid nitrogen until its temperature reaches -132 °C. Assuming the pressure remains constant, what is the volume of the cooled balloon?
 a. 0.628 L b. 0.781 L c. 1.24 L d. 1.49 L e. 6.96 L

4.

Avogadro's hypothesis states that equal volumes of gases under the same conditions of temperature and pressure have equal ____.
 a. densities b. particle velocities c. molar masses d. numbers of particles e. masses

5.

Which of the following relationships are true for gases?

 1. The number of moles of a gas is directly proportional to its volume (at constant pressure). 2. The pressure of a gas is inversely proportional to its temperature in Kelvins (at constant volume). 3. The volume of a gas is directly proportional to its pressure (at constant temperature).
 a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 2 and 3

6.

If 3.67 g CO2 gas is introduced into an evacuated 2.50 L flask at 65 °C, what is the pressure inside the flask? (R = 0.08206 L·atm/mol·K)
 a. 0.178 atm b. 0.445 atm c. 0.925 atm d. 40.7 atm e. 496 atm

7.

A mass of 1.663 g of an unknown gas is introduced into an evacuated 2.00 L flask. If the pressure in the flask is 0.544 atm at 78 °C, which of the following gases might be in the flask? (R = 0.08206 L·atm/mol·K)
 a. N2 b. C2H2 c. NH3 d. HCl e. N2O

8.

What volume of O2, measured at 91.2 °C and 743 mm Hg, will be produced by the decomposition of 4.88 g KClO3? (R = 0.08206 L·atm/mol·K)

2 KClO3(s) ® 2 KCl(s) + 3 O2(g)
 a. 0.305 L b. 1.22 L c. 1.83 L d. 24.0 L e. 37.4 L

9.

Ammonia gas is synthesized according to the balanced equation below.

N2(g) + 3 H2(g) ® 2 NH3(g)

If 2.75 L N2 react with 7.75 L H2, what is the theoretical yield (in liters) of NH3? Assume that the volumes of reactants and products are measured at the same temperature and pressure.
 a. 2.75 L b. 5.17 L c. 5.50 L d. 10.5 L e. 15.5 L

10.

The empirical formula of a certain hydrocarbon is CH2. When 0.120 mole of the hydrocarbon is completely combusted with excess oxygen, 17.7 L CO2 gas is produced at 27 °C and 1.00 atm. What is the molecular formula of the hydrocarbon? (R = 0.08206 L·atm/mol·K)
 a. C2H2 b. C2H4 c. C3H6 d. C5H10 e. C6H12

11.

An unknown gaseous hydrocarbon contains 85.63 % C. Its density is 0.426 g/L at 0.465 atm and 373 K. What is the molecular formula of the gas? (R = 0.08206 L·atm/mol·K)
 a. C2H4 b. C3H6 c. C4H8 d. C5H10 e. C6H12

12.

Carbon monoxide reacts with oxygen to form carbon dioxide.

2 CO(g) + O2(g) ® 2 CO2(g)

In a 1.00 L flask, 2.40 atm of CO reacts with 4.50 atm of O2. Assuming that the temperature remains constant, what is the final pressure in the flask?
 a. 1.20 atm b. 2.40 atm c. 3.30 atm d. 3.60 atm e. 5.70 atm

13.

A mixture of He and O2 is placed in a 4.00 L flask at 32 °C. The partial pressure of the He is 2.7 atm and the partial pressure of the O2 is 1.4 atm. What is the mole fraction of O2?
 a. 0.224 b. 0.341 c. 0.481 d. 0.518 e. 0.659

14.

Which of the following are postulates of kinetic-molecular theory of gases?

 1. The distance between gas molecules is large in comparison to their size. 2. Gas molecules are in constant, random motion. 3. The kinetic energy of gas particles is proportional to the Kelvin temperature.
 a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

15.

What is the root-mean-square velocity of ethane molecules (C2H6) at 273 K?
 a. 15.0 m/s b. 47.2 m/s c. 275 m/s d. 476 m/s e. 652 m/s

16.

Place the following gases in order of increasing average velocity at 325 K: Ar, Ne, N2, and SO2.
 a. Ar < Ne < N2 < SO2 b. Ne < Ar < N2 < SO2 c. N2 < SO2 < Ne < Ar d. SO2 < Ar < N2 < Ne e. Ar = Ne = N2 = SO2

17.

The average velocity of a gas molecule is
 a. inversely proportional to its kinetic energy. b. directly proportional to the gas constant, R. c. directly proportional to the square root of its temperature in K. d. inversely proportional to the square of its mass. e. directly proportional to the square root of its mass.

18.

Carbon monoxide gas diffuses through a barrier at a rate of 0.480 mL/minute. If an unknown gas diffuses through the same barrier at a rate of 0.277 mL/minute, what is the molar mass of the gas?
 a. 9.33 g/mol b. 21.3 g/mol c. 36.9 g/mol d. 44.01 g/mol e. 84.1 g/mol

19.

Non-ideal behavior for a gas is most likely to be observed under conditions of
 a. high temperature and low pressure. b. high temperature and high pressure. c. low temperature and low pressure. d. standard temperature and pressure. e. low temperature and high pressure.

20.

One way in which real gases differ from ideal gases is that the molecules of a real gas
 a. are attracted to each other. b. are liquids or solids above 273.15 K. c. are always polar. d. move in circles rather than straight paths. e. have no kinetic energy.

21.

If 4.00 g S8 react with 4.25 L O2 at 39 °C and 1.00 atm, what is the maximum mass of SO3 produced? (R = 0.08206 L·atm/mol·K)

S8(s) + 12 O2(g) ® 8 SO3(g)
 a. 2.83 g b. 8.86 g c. 9.99 g d. 13.3 g e. 19.9 g

22.

If a gas effuses 1.618 times faster than Kr, what is its molar mass?
 a. 18.02 g/mol b. 28.01 g/mol c. 32.01 g/mol d. 51.79 g/mol e. 65.88 g/mol