Class activity –gases NAME:…………………………….
1. Which of the following equations shows an incorrect relationship between pressures given in terms of different units?
A) 1.20 atm = 122 kPa
B) 152 mm Hg = 2.03 × 104Pa
C) 0.760 atm = 578 mm Hg
D) 1.0 torr = 2.00 mm Hg
E) 1.00 atm = 760 torr
Answer: D
Diff: 2 Page Ref: Sec. 10.2
2) The volume of an ideal gas is zero at ______.
A) 0 °C
B) -45 °F
C) -273 K
D) -363 K
E) -273 °C
Answer: E
Diff: 1 Page Ref: Sec. 10.3
3) The molar volume of a gas at STP is ______L.
A) 0.08206
B) 62.36
C) 1.00
D) 22.4
E) 14.7
Answer: D
Diff: 1 Page Ref: Sec. 10.4
4) How many moles of gas are there in a 45.0 L container at 25.0°C and 500.0 mm Hg?
A) 0.630
B) 6.11
C) 18.4
D) 1.21
E) 207
Answer: D
Diff: 3 Page Ref: Sec. 10.4
5) The volume of a sample of gas (2.49 g) was 752 mL at 1.98 atm and 62°C. The gas is ______.
A) SO2
B) SO3
C) NH3
D) NO2
E) Ne Answer: D
6) The density of ______is 0.900 g/L at STP.
A) CH4
B) Ne
C) CO
D) N2
E) NO
Answer: B
7) A mixture of Xe, Kr, and Ar has a total pressure of 6.70 atm. What is the mole fraction of Kr if the partial pressures of Xe and Ar are 1.60 atm and 2.80 atm, respectively.
A) 0.174
B) 0.256
C) 0.343
D) 0.481
E) 0.570
Answer: C
8) The root-mean-square speed of H2S at 26.0°C is ______m/sec.
A) 334
B) 62.4
C) 468
D) 751
E) 214
Answer: C
9) Arrange the following gases in order of increasing average molecular speed at 25°C.
He, O2, CO2, N2
A) He < N2 < O2 < CO2
B) He < O2 < N2 < CO2
C) CO2 < O2 < N2 < He
D) CO2 < N2 < O2 < He
E) CO2 < He < N2O2
Answer: C
10) A mixture of two gases was allowed to effuse from a container. One of the gases escaped from the container 1.43 times as fast as the other one. The two gases could have been______.
A) CO and SF6
B) O2 and Cl2
C) CO and CO2
D) Cl2 and SF6
E) O2 and SF6 Answer: D
11) A sample of a gas (5.0 mol) at 1.0 atm is expanded at constant temperature from 10 L to 15 L. The final pressure is ______atm.
A) 1.5
B) 7.5
C) 0.67
D) 3.3
E) 15
Answer: C
12) If 50.75 g of a gas occupies 10.0 L at STP, 129.3 g of the gas will occupy ______L at STP.
A) 3.92
B) 50.8
C) 12.9
D) 25.5
E) 5.08
Answer: D
13) A sample of a gas originally at 25°C and 1.00 atmpressure in a 2.5 L container is subject to a pressure of 0.85 atm and a temperature of 15°C. The final volume of the gas is ______L.
A) 3.0
B) 2.8
C) 2.6
D) 2.1
E) 0.38
Answer: B
14)The molecular weight of a gas that has a density of 7.10 g/L at 25.0°C and 1.00 atm pressure is ______g/mol.
A) 174
B) 14.6
C) 28.0
D) 5.75 × 10-3
E) 6.85 × 10-2 Answer: A
15) Automobile air bags use the decomposition of sodium azide as their source of gas for rapid inflation:
2NaN3 (s) → 2Na (s) + 3N2 (g).
What mass (g) of NaN3 is required to provide 40.0 L of N2 at 25.0°C and 763 torr?
A) 1.64
B) 1.09
C) 160
D) 71.1
E) 107 Answer: D
16)What volume (L) of NH3 gas at STP is produced by the complete reaction of 7.5 g of H2O according to the following reaction?
Mg3N2 (s) + 6H2O (l) → 3Mg(OH)2 (aq) + 2NH3 (g)
A) 3.1
B) 9.3
C) 19
D) 28
E) 0.32
Answer: A
Diff: 4 Page Ref: Sec. 10.5
17)The pressure in a 12.2 L vessel that contains 2.34 g of carbon dioxide, 1.73 g of sulfur dioxide, and 3.33 g of argon, all at 42 °C is ______mm Hg.
A) 263
B) 134
C) 395
D) 116
E) 0.347
Answer: A
Diff: 3 Page Ref: Sec. 10.6
18)A sample of H2 gas (2.0 L) at 3.5 atm was combined with 1.5 L of N2 gas at 2.6 atm pressure at a constant temperature of 25°C into a 7.0 L flask. The total pressure in the flask is ______atm. Assume the initial pressure in the flask was 0.00 atm and the temperature upon mixing was 25°C.
A) 0.56
B) 2.8
C) 1.0
D) 1.6
E) 24
Answer: D
19)A balloon originally had a volume of 4.39 L at 44°C and a pressure of 729 torr. The balloon must be cooled to ______°C to reduce its volume to 3.78 L (at constant pressure).
A) 38.0
B) 0.00
C) 72.9
D) 273
E) 546
Answer: B