Q: A high-performance bicycle tire has a pressure of 132 psi. What is the pressure in mmHg? (1 atm = 14.70 psi, 1 atm = 760 mmHg)

$$132 \times \frac{1}{14.70} \times 760 = 6,826$$ mmHg

Q: A sample of argon gas occupied 105 mL at 0.871 atm. If the temperature remains constant, what is the volume (in L) at 197 Torr? (1 atm = 760 Torr)

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.871 \times 0.105}{197/760} = 0.36$$ L

Q: A 425 mL sample of fluorine gas is heated from 22 °C to 185 °C at constant pressure. What is the final volume? (Use Charles's Law)

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 0.425 \times \frac{458}{295} = 0.66$$ L

Q: A newly discovered gas has a density of 2.39 g/L at 23.0 °C and 715 mmHg. What is the molar mass of the gas? (R = 0.08206 L·atm/mol·K)

$$M = \frac{dRT}{P} = \frac{2.39 \times 0.08206 \times 296}{715/760} = 81.2 g/$$mol

Question 1

A high-performance bicycle tire has a pressure of 132 psi. What is the pressure in mmHg? (1 atm = 14.70 psi, 1 atm = 760 mmHg)

Accepted Answer

$$132 	imes \frac{1}{14.70} 	imes 760 = 6,826$$ mmHg

Question 2

A sample of argon gas occupied 105 mL at 0.871 atm. If the temperature remains constant, what is the volume (in L) at 197 Torr? (1 atm = 760 Torr)

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{0.871 	imes 0.105}{197/760} = 0.36$$ L

Question 3

Which of the following best explains why gases are highly compressible compared to solids and liquids?

Accepted Answer

Gas molecules are far apart and have negligible volume compared to the container.

Question 4

A 425 mL sample of fluorine gas is heated from 22 °C to 185 °C at constant pressure. What is the final volume? (Use Charles's Law)

Accepted Answer

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 0.425 	imes \frac{458}{295} = 0.66$$ L

Question 5

Which of the following statements about the kinetic molecular theory is correct?

Accepted Answer

Gas molecules are in constant, random motion and collisions are elastic.

Question 6

A tank with a fixed volume of 438 L is filled with 0.885 kg O$$_2. $$Calculate the pressure of oxygen at 21.0 °C. (R = 0.08206 L·atm/mol·K, M$$_{O_2$} = 32.00 g/$$mol)

Accepted Answer

$$n = \frac{885}{32.00} = 27.7$$ mol; $$P = \frac{nRT}{V} = \frac{27.7 	imes 0.08206 	imes 294}{438} = 1.52$$ atm

Question 7

A gas occupies 10.0 L at 44.1 psi and 27°C. What volume will it occupy at STP? (1 atm = 14.70 psi, STP: 0°C, 1 atm)

Accepted Answer

$$P_1V_1/T_1$ = P_2V_2/T_2$; V_2$ = V_1$ \frac{P_1$}{P_2$} \frac{T_2$}{T_1$} = 10.0 	imes \frac{44.1/14.70}{1} 	imes \frac{273.15}{300.15} = 8.18 L$$

Question 8

A newly discovered gas has a density of 2.39 g/L at 23.0 °C and 715 mmHg. What is the molar mass of the gas? (R = 0.08206 L·atm/mol·K)

Accepted Answer

$$M = \frac{dRT}{P} = \frac{2.39 	imes 0.08206 	imes 296}{715/760} = 81.2 g/$$mol

Question 9

Which of the following best describes Dalton's Law of Partial Pressures?

Accepted Answer

The total pressure of a mixture of unreacting gases is the sum of the partial pressures of the individual gases.

Question 10

Oxygen gas generated in the decomposition of potassium chlorate is collected over water. The volume of the gas collected at 24.0 °C and atmospheric pressure of 762 mmHg is 128 mL. The vapor pressure of water at 24.0 °C is 22.4 mmHg. What is the pressure of the dry oxygen gas?

Accepted Answer

$$P_{O_2$} = P_{total} - P_{H_2O} = 762 - 22.4 = 739.6$$ mmHg

Question 11

A sample of nitrogen gas in a 1.85 L container exerts a pressure of 1.45 atm at 25°C. What is the pressure if the volume of the container is increased to 2.05 L and the temperature is raised to 351°C?

Accepted Answer

$$P_2$$ = $$P_1$$ \frac{$$V_1$$}{$$V_2$$} \frac{$$T_2$$}{$$T_1$$} = 1.45 	imes \frac{1.85}{2.05} 	imes \frac{624}{298} = 2.80$$ atm

Question 12

Which of the following is a key assumption of the ideal gas law?

Accepted Answer

Gas molecules do not attract or repel each other.

Question 13

A 500.0 mL flask containing a sample of octane vapor is placed in a boiling water bath in Denver, where the atmospheric pressure is 634 mm Hg and water boils at 95.0 °C. The mass of the vapor required to fill the flask is 1.57 g. What is the molar mass of octane? (R = 0.08206 L·atm/mol·K, 1 atm = 760 mmHg)

Accepted Answer

$$n = \frac{PV}{RT} = \frac{(634/760) 	imes 0.500}{0.08206 	imes 368} = 0.014$$ mol; M = \frac{1.57}{0.014} = 112$ g/mol

Question 14

Which of the following best explains why real gases deviate from ideal behavior at high pressures?

Accepted Answer

The volume of gas molecules becomes significant compared to the container.

Question 15

According to Graham's Law, which gas will effuse faster: H$$_2 (M = 2.02 g/$$mol) or O$$_2 (M = 32.00 g/$$mol)? By what factor?

Accepted Answer

$$	ext{Rate}_{H_2$}/	ext{Rate}_{O_2$} = \sqrt{\frac{32.00}{2.02}} = 3.98$$

Question 16

A gas mixture contains 2.0 mol N$$_2$$, 1.0 mol O$$_2$$, and 1.0 mol Ar in a 10.0 L container at 300 K. What is the partial pressure of O$$_2$$? (R = 0.08206 L·atm/mol·K)

Accepted Answer

$$P_{O_2$} = \frac{nRT}{V} = \frac{1.0 	imes 0.08206 	imes 300}{10.0} = 2.46$$ atm

Chapter 6: Gases – Properties, Laws, and Applications

Guida di studio - Domande di pratica

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