Q: A sample of oxygen gas occupies 5.00 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm at constant temperature, what will be the new volume?

$$V_2$$ = $$V_1$$ \times \dfrac{$$P_1$$}{$$P_2$$} = 5.00\,\mathrm{L} \times \dfrac{1.00}{2.00} = 2.50\,\mathrm{L}$$

Q: A weather balloon is filled with 10.0 L of helium at 1.00 atm and 25°C. If the balloon rises to a region where the pressure is 0.500 atm and the temperature is -25°C, what is the new volume? (Assume ideal gas behavior.)

$$V_2$$ = $$V_1$$ \times \dfrac{$$P_1$$}{$$P_2$$} \times \dfrac{$$T_2$$}{$$T_1$$} = 10.0\,\mathrm{L} \times \dfrac{1.00}{0.500} \times \dfrac{248}{298} = 16.7\,\mathrm{L}$$

Q: A 2.00 L container holds 0.100 mol of nitrogen gas at 27°C. What is the pressure inside the container? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

$$P = \dfrac{nRT}{V} = \dfrac{0.100 \times 0.0821 \times 300}{2.00} = 1.23\,\mathrm{atm}$$

Q: A sample of gas has a volume of 3.00 L at 1.00 atm and 273 K. How many moles of gas are present?

$$n = \dfrac{PV}{RT} = \dfrac{1.00 \times 3.00}{0.0821 \times 273} = 0.134\,\mathrm{mol}$$

Q: A mixture contains 2.0 mol of O$$_2$$ and 3.0 mol of N$$_2 in a 10.0 L $$container at 300 K. What is the total pressure? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

$$P = \dfrac{nRT}{V} = \dfrac{5.0 \times 0.0821 \times 300}{10.0} = 12.3\,\mathrm{atm}$$

Q: Which of the following is the correct expression for Dalton's Law of Partial Pressures?

$$P_{\text{total}} = P_1$ + P_2$ + P_3$ + \ldots$$

Question 1

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

Accepted Answer

Gas particles are far apart with negligible intermolecular forces, allowing them to be compressed.

Question 2

A sample of oxygen gas occupies 5.00 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm at constant temperature, what will be the new volume?

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \dfrac{$$P_1$$}{$$P_2$$} = 5.00\,\mathrm{L} 	imes \dfrac{1.00}{2.00} = 2.50\,\mathrm{L}$$

Question 3

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

Accepted Answer

Gas particles exert attractive forces on each other.

Question 4

A weather balloon is filled with 10.0 L of helium at 1.00 atm and 25°C. If the balloon rises to a region where the pressure is 0.500 atm and the temperature is -25°C, what is the new volume? (Assume ideal gas behavior.)

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \dfrac{$$P_1$$}{$$P_2$$} 	imes \dfrac{$$T_2$$}{$$T_1$$} = 10.0\,\mathrm{L} 	imes \dfrac{1.00}{0.500} 	imes \dfrac{248}{298} = 16.7\,\mathrm{L}$$

Question 5

Which gas law explains why a sealed bag of chips expands as you drive up a mountain?

Accepted Answer

Atmospheric pressure decreases with altitude, so the pressure inside the bag exceeds the outside, causing expansion.

Question 6

A 2.00 L container holds 0.100 mol of nitrogen gas at 27°C. What is the pressure inside the container? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P = \dfrac{nRT}{V} = \dfrac{0.100 	imes 0.0821 	imes 300}{2.00} = 1.23\,\mathrm{atm}$$

Question 7

Which of the following statements about STP (Standard Temperature and Pressure) is correct?

Accepted Answer

STP is 0°C and 1.00 atm.

Question 8

A sample of gas has a volume of 3.00 L at 1.00 atm and 273 K. How many moles of gas are present?

Accepted Answer

$$n = \dfrac{PV}{RT} = \dfrac{1.00 	imes 3.00}{0.0821 	imes 273} = 0.134\,\mathrm{mol}$$

Question 9

Which of the following best explains why water boils at a lower temperature at higher altitudes?

Accepted Answer

Atmospheric pressure is lower, so water molecules require less energy to escape into the gas phase.

Question 10

A mixture contains 2.0 mol of O$$_2$$ and 3.0 mol of N$$_2 in a 10.0 L $$container at 300 K. What is the total pressure? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P = \dfrac{nRT}{V} = \dfrac{5.0 	imes 0.0821 	imes 300}{10.0} = 12.3\,\mathrm{atm}$$

Question 11

Which of the following is the correct expression for Dalton's Law of Partial Pressures?

Accepted Answer

$$P_{	ext{total}} = P_1$ + P_2$ + P_3$ + \ldots$$

Question 12

A gas sample is collected over water at 25°C. The total pressure is 755 mmHg, and the vapor pressure of water at 25°C is 24 mmHg. What is the pressure of the dry gas?

Accepted Answer

$$P_{	ext{gas}} = P_{	ext{total}} - P$$_{	ext{H}$$_2O} = 755\,\mathrm{mmHg} - 24\,\mathrm{mmHg} = 731\,\mathrm{mmHg}$$

Question 13

Which of the following gases will effuse the fastest under identical conditions?

Accepted Answer

Helium (He)

Question 14

A 5.00 L tank contains 2.00 mol of an ideal gas at 400 K. What is the pressure in the tank? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P = \dfrac{nRT}{V} = \dfrac{2.00 	imes 0.0821 	imes 400}{5.00} = 13.1\,\mathrm{atm}$$

Question 15

Which of the following best describes the relationship between temperature and kinetic energy of a gas?

Accepted Answer

As temperature increases, the average kinetic energy of gas particles increases.

Question 16

A gas occupies 8.00 L at 2.00 atm and 300 K. What volume will it occupy at 1.00 atm and 400 K?

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \dfrac{$$P_1$$}{$$P_2$$} 	imes \dfrac{$$T_2$$}{$$T_1$$} = 8.00\,\mathrm{L} 	imes 2.00 	imes \dfrac{400}{300} = 21.3\,\mathrm{L}$$

Question 17

Which of the following is a correct statement of Avogadro's Law?

Accepted Answer

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Question 18

A 1.00 L flask contains 0.040 mol of CO$$_2 at 27$$°C. What is the pressure in the flask? $$(R = 0.0821\,\mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P = \dfrac{nRT}{V} = \dfrac{0.040 	imes 0.0821 	imes 300}{1.00} = 0.985\,\mathrm{atm}$$

Question 19

Which of the following best explains why a balloon filled with helium rises in air?

Accepted Answer

Helium is less dense than air, so the buoyant force pushes the balloon upward.

Question 20

A gas sample is cooled from 300 K to 150 K at constant pressure. What happens to the volume?

Accepted Answer

The volume decreases by half.

Ch 8 - Gases: Properties, Laws, and Calculations

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