Q: A sample of oxygen gas is collected over water at 25°C. The total pressure is 755 mmHg. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of the oxygen gas?

$$755\,-\,23.8\,=\,731.2\,\text{mmHg}$$

Q: A 3.24-L basketball is inflated to a total pressure of 24.3 psi at 25.0°C. How many moles of gas are inside the ball? ($$1\,\text{atm}\,=\,14.7\,\text{psi}$$, $$R=0.08206\,\text{L}\cdot\text{atm}/\text{mol}\cdot\text{K})$$

$$n=\dfrac{PV}{RT}=\dfrac{(24.3/14.7)\times3.24}{0.08206\times(25+273)}=0.4\,\text{mol}$$

Q: A mixture contains 0.50 mol He and 1.50 mol Ne in a 10.0 L container at 300 K. If the total pressure is 2.0 atm, what is the partial pressure of Ne?

$$P_{\text{Ne}}=X_{\text{Ne}}P_T=\dfrac{1.50}{0.50+1.50}\times2.0=1.5\,\text{atm}$$

Q: A 15.0 L container holds 0.508 mol O$$_2 at 303 K. $$What is the pressure exerted by the gas? ($$R=0.08206\,\text{L}\cdot\text{atm}/\text{mol}\cdot\text{K})$$

$$P=\dfrac{nRT}{V}=\dfrac{0.508\times0.08206\times303}{15.0}=0.842\,\text{atm}$$

Q: A gas sample at 1.00 atm and 273 K occupies 22.4 L. If the pressure is doubled and the temperature is increased to 546 K, what is the new volume?

$$V_2$$=\dfrac{P_1V_1T_2}{P_2T_1}=\dfrac{1.00\times22.4\times546}{2.00\times273}=22.4\,\text{L}$$

Q: A mixture of gases contains 2.0 mol O$$_2$$, 1.0 mol N$$_2$$, and 1.0 mol CO$$_2 in a 10.0 L $$container at 300 K. If the total pressure is 4.0 atm, what is the partial pressure of O$$_2$$?

$$P_{O_2$}=X$$_{O_2}$$P_T=\dfrac{2.0}{2.0+1.0+1.0}\times4.0=2.0\,\text{atm}$$

Question 1

Which of the following statements best explains why gases are compressible, while solids and liquids are not?

Accepted Answer

Gas particles have negligible volume compared to the container, leaving large amounts of empty space between them.

Question 2

A sample of oxygen gas is collected over water at 25°C. The total pressure is 755 mmHg. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of the oxygen gas?

Accepted Answer

$$755\,-\,23.8\,=\,731.2\,	ext{mmHg}$$

Question 3

Which of the following correctly describes the relationship between pressure and volume for a gas at constant temperature and amount?

Accepted Answer

Pressure is inversely proportional to volume.

Question 4

A 3.24-L basketball is inflated to a total pressure of 24.3 psi at 25.0°C. How many moles of gas are inside the ball? ($$1\,	ext{atm}\,=\,14.7\,	ext{psi}$$, $$R=0.08206\,	ext{L}\cdot	ext{atm}/	ext{mol}\cdot	ext{K})$$

Accepted Answer

$$n=\dfrac{PV}{RT}=\dfrac{(24.3/14.7)	imes3.24}{0.08206	imes(25+273)}=0.4\,	ext{mol}$$

Question 5

Which of the following is NOT an assumption of the kinetic molecular theory for ideal gases?

Accepted Answer

Gas molecules lose energy during collisions.

Question 6

A mixture contains 0.50 mol He and 1.50 mol Ne in a 10.0 L container at 300 K. If the total pressure is 2.0 atm, what is the partial pressure of Ne?

Accepted Answer

$$P_{	ext{Ne}}=X_{	ext{Ne}}P_T=\dfrac{1.50}{0.50+1.50}	imes2.0=1.5\,	ext{atm}$$

Question 7

Which of the following gases will have the highest rate of effusion through a small hole at the same temperature?

Accepted Answer

H$$_2$$

Question 8

A 15.0 L container holds 0.508 mol O$$_2 at 303 K. $$What is the pressure exerted by the gas? ($$R=0.08206\,	ext{L}\cdot	ext{atm}/	ext{mol}\cdot	ext{K})$$

Accepted Answer

$$P=\dfrac{nRT}{V}=\dfrac{0.508	imes0.08206	imes303}{15.0}=0.842\,	ext{atm}$$

Question 9

Which of the following best describes the effect of increasing temperature on the average kinetic energy and speed of gas molecules?

Accepted Answer

Both average kinetic energy and speed increase.

Question 10

A gas sample at 1.00 atm and 273 K occupies 22.4 L. If the pressure is doubled and the temperature is increased to 546 K, what is the new volume?

Accepted Answer

$$V_2$$=\dfrac{P_1V_1T_2}{P_2T_1}=\dfrac{1.00	imes22.4	imes546}{2.00	imes273}=22.4\,	ext{L}$$

Question 11

Which of the following is the correct expression for the density of a gas using the ideal gas law?

Accepted Answer

$$d=\dfrac{MP}{RT}$$

Question 12

A mixture of gases contains 2.0 mol O$$_2$$, 1.0 mol N$$_2$$, and 1.0 mol CO$$_2 in a 10.0 L $$container at 300 K. If the total pressure is 4.0 atm, what is the partial pressure of O$$_2$$?

Accepted Answer

$$P_{O_2$}=X$$_{O_2}$$P_T=\dfrac{2.0}{2.0+1.0+1.0}	imes4.0=2.0\,	ext{atm}$$

Question 13

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

Accepted Answer

The volume occupied by gas molecules becomes significant compared to the container volume.

Question 14

According to Graham's law, how does the rate of effusion of H$$_2$$ compare to that of O$$_2$$?

Accepted Answer

$$	ext{Rate}_{H_2$}/	ext{Rate}_{O_2$}=\sqrt{M_{O_2$}/M_{H_2$}}=\sqrt{32/2}=4$$

Question 15

Which of the following gases has the greatest density at STP?

Accepted Answer

Cl$$_2$$

Question 16

A sample of gas at 1.00 atm and 273 K has a molar mass of 44.0 g/mol. What is its density?

Accepted Answer

$$d=\dfrac{MP}{RT}=\dfrac{44.0	imes1.00}{0.08206	imes273}=1.97\,	ext{g/L}$$

Question 17

Which of the following is the correct form of the combined gas law?

Accepted Answer

$$\dfrac{P_1V_1}{T_1$}=\dfrac{P_2V_2}{T_2$}$$

Question 18

A gas mixture contains 1.0 mol He and 1.0 mol Ne. The total pressure is 3.0 atm. What are the partial pressures of Ne and He?

Accepted Answer

$$P_{He}=1.5\,	ext{atm},\;P_{Ne}=1.5\,	ext{atm}$$

Question 19

Which of the following best describes the effect of intermolecular attractions on the pressure of a real gas at low temperature?

Accepted Answer

The pressure is lower than predicted by the ideal gas law.

Chapter 8: Gases – Properties, Laws, and Behavior

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