Q: A sample of nitrogen gas occupies 2.50 L at 1.00 atm and 300 K. What will the volume be if the pressure is increased to 2.00 atm at constant temperature?

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 \times 2.50}{2.00} = 1.25\ \mathrm{L}$$

Q: A 5.00 g sample of oxygen gas ($$O_2) is $$collected in a 10.0 L container at 27°C. What is the pressure in the container? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

$$P = \frac{nRT}{V} = \frac{0.156\times 0.0821 \times 300}{10.0} = 0.384\ \mathrm{atm}$$

Q: A mixture contains 2.0 mol of $$N_2$$ and 3.0 mol of $$O_2 in a 10.0 L $$container at 300 K. What is the partial pressure of $$O_2$$? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

$$P_{O_2$} = \frac{3.0}{5.0} \times P_{total}$$, where $$P_{total} = \frac{5.0 \times 0.0821 \times 300}{10.0} = 12.315\ \mathrm{atm}$$, so $$P_{O_2$} = 7.389\ \mathrm{atm}$$

Question 1

Ice cores are used to study Earth's ancient atmosphere. Which of the following best explains how scientists determine the age of air trapped in different layers of an ice core?

Accepted Answer

The age is determined by the position in the glacier, with deeper layers being older because glaciers form from the accumulation of snow over time, compacting lower layers.

Question 2

Which of the following statements about the Boltzmann distribution of molecular speeds is correct?

Accepted Answer

At a given temperature, heavier molecules have a lower average speed than lighter molecules.

Question 3

Which of the following is NOT a postulate of the kinetic molecular theory of gases?

Accepted Answer

Gas particles exert attractive and repulsive forces on each other.

Question 4

A sample of nitrogen gas occupies 2.50 L at 1.00 atm and 300 K. What will the volume be if the pressure is increased to 2.00 atm at constant temperature?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 	imes 2.50}{2.00} = 1.25\ \mathrm{L}$$

Question 5

Which of the following units is NOT a standard unit of pressure?

Accepted Answer

$$\mathrm{J}$$

Question 6

A 5.00 g sample of oxygen gas ($$O_2) is $$collected in a 10.0 L container at 27°C. What is the pressure in the container? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{0.156	imes 0.0821 	imes 300}{10.0} = 0.384\ \mathrm{atm}$$

Question 7

Which of the following best describes the role of water vapor density in the strengthening of hurricanes?

Accepted Answer

Higher water vapor density provides more latent heat upon condensation, fueling stronger hurricanes.

Question 8

A mixture contains 2.0 mol of $$N_2$$ and 3.0 mol of $$O_2 in a 10.0 L $$container at 300 K. What is the partial pressure of $$O_2$$? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$P_{O_2$} = \frac{3.0}{5.0} 	imes P_{total}$$, where $$P_{total} = \frac{5.0 	imes 0.0821 	imes 300}{10.0} = 12.315\ \mathrm{atm}$$, so $$P_{O_2$} = 7.389\ \mathrm{atm}$$

Question 9

Which of the following molecules can form hydrogen bonds with water?

Accepted Answer

$$NH_3$$

Question 10

Rank the following intermolecular forces in order of increasing strength for small molecules: dispersion, hydrogen bonding, dipole-dipole.

Accepted Answer

Dispersion \u003c dipole-dipole \u003c hydrogen bonding

Question 11

Which of the following statements about dispersion forces is correct?

Accepted Answer

Dispersion forces increase with increasing molecular size.

Question 12

Which of the following best explains why water has a high enthalpy of vaporization ($$\Delta H_{vap}$$)?

Accepted Answer

Water molecules form strong hydrogen bonds, requiring more energy to separate them during vaporization.

Question 13

Which of the following is a real-life application that depends on the high $$\Delta H_{vap} of $$water?

Accepted Answer

The use of water as a coolant in car radiators.

Question 14

Which of the following best describes how vapor pressure is measured?

Accepted Answer

By measuring the pressure exerted by a vapor in equilibrium with its liquid in a closed container.

Question 15

Which of the following best explains the relationship between vapor pressure and the strength of intermolecular forces?

Accepted Answer

Stronger intermolecular forces result in lower vapor pressure.

Question 16

Which of the following is required for a molecule to exhibit hydrogen bonding?

Accepted Answer

The molecule must contain a hydrogen atom bonded to a highly electronegative atom such as N, O, or F.

Question 17

Which of the following best describes a foam?

Accepted Answer

A foam is a colloidal dispersion of a gas in a liquid.

Question 18

Which of the following is an example of hydrogen bonding playing a critical role in living systems?

Accepted Answer

The double helix structure of DNA is stabilized by hydrogen bonds between base pairs.

Question 19

A gas mixture contains 1.0 mol $$He$$, 2.0 mol $$Ne$$, and 3.0 mol $$Ar at a $$total pressure of 3.0 atm. What is the mole fraction of $$Ne$$ and its partial pressure?

Accepted Answer

Mole fraction of $$Ne is$$ $$\frac{2.0}{6.0} = 0.333$$, partial pressure is $$0.333 	imes 3.0 = 1.0\ \mathrm{atm}$$

Question 20

A 2.00 L flask contains 0.100 mol of $$CO_2 at 27$$°C. What is the density of $$CO_2 in $$the flask? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$}$$; $$M_{CO_2$} = 44.0\ \mathrm{g\cdot $$mol^{-1}$$})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{0.100 	imes 0.0821 	imes 300}{2.00} = 1.23\ \mathrm{atm}$$; $$d = \frac{PM}{RT} = \frac{1.23 	imes 44.0}{0.0821 	imes 300} = 2.20\ \mathrm{g\cdot L$$^{-1}$$}$$

Chemistry 1770 Final Study Guide: Gases and Intermolecular Forces

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