Chapter 12

Calculate the ratio of effusion rates for nitrogen \(\left(\mathrm{N}_{2}\right)\) and neon (Ne).

Challenge What is the rate of effusion for a gas that has a molar mass twice that of a gas that effuses at a rate of 3.6 \(\mathrm{mol} / \mathrm{min}\) ?

What is the partial pressure of hydrogen gas in a mixture of hydrogen and helium if the total pressure is 600 \(\mathrm{mm} \mathrm{Hg}\) and the partial pressure of helium is 439 \(\mathrm{mm} \mathrm{Hg?}\)

Find the total pressure for a mixture that contains four gases with partial pressures of \(5.00 \mathrm{kPa}, 4.56 \mathrm{kPa}, 3.02 \mathrm{kPa},\) and 1.20 \(\mathrm{kPa}\)

Find the partial pressure of carbon dioxide in a gas mixture with a total pressure of 30.4 \(\mathrm{kPa}\) if the partial pressures of the other two gases in the mixture are 16.5 \(\mathrm{kPa}\) and 3.7 \(\mathrm{kPa}\) .

Challenge Air is a mixture of gases. By percentage, it is roughly 78 percent nitrogen, 21 percent oxygen, and 1 percent argon. (There are trace amounts of many other gases in air. If the atmospheric pressure is 760 \(\mathrm{mm}\) Hg, what are the partial pressures of nitrogen, oxygen, and argon in the atmosphere?

Explain Use the kinetic theory to explain the behavior of gases.

Describe how the mass of a gas particle affects its rate of effusion and diffusion.

Explain why the container of water must be inverted when a gas is collected by displacement of water.

Calculate Suppose two gases in a container have a total pressure of 1.20 atm. What is the pressure of Gas \(B\) if the partial pressure of Gas A is 0.75 atm?

Infer whether or not temperature has any effect on the diffusion rate of a gas. Explain your answer.

Explain what determines a substance's state at a given temperature.

Compare and contrast intermolecular forces and describe intramolecular forces.

Evaluate Which of the molecules listed below can form hydrogen bonds? For which of the molecules would dispersion forces be the only intermolecular force? Give reasons for your answers. $$\text { a. }\mathrm{H}_{2} \quad \text { b. } \mathrm{H}_{2} \mathrm{S} \quad \text { c. } \mathrm{HCl} \quad \text { d. } \mathrm{HF}$$

Intepret Data In a methane molecule \(\left(\mathrm{H}_{4}\right),\) there four single covalent bonds. In an octane molecule \(\left(\mathrm{C}_{8} \mathrm{H}_{18}\right)\) , there are 25 single covalent bonds. How does the number of bonds affect the dispersion forces in samples of methane and octane? Which compound is a gas at room temperature? Which is a liquid?

Contrast the arrangement of particles in solids and liquids.

Describe the factors that affect viscosity.

Explain why soap and water are used to clean clothing instead of water alone.

Compare a unit cell and a crystal lattice.

Describe the difference between a molecular solid and a covalent network solid.

Explain why water forms a meniscus when it is in a graduated cylinder.

Infer why the surface of mercury in a thermometer is convex, that is, the surface is higher at the center.

Predict which solid is more likely to be amorphous - one formed by allowing a molten material to cool slowly to room temperature one formed by quickly cooling the same material in an ice bath.

Design an experiment to compare the relative abilities of water and isopropyl alcohol to support skipping stones. Include a prediction about which liquid will be better, along with a brief explanation of your prediction.

Explain how the addition or removal of energy can cause a phase change.

Explain the difference between the processes of melting and freezing.

Compare deposition and sublimation.

Compare and contrast sublimation and evaporation.

Describe the information that a phase diagram supplies.

Explain what the triple point and the critical point on a phase diagram represent.

What is an elastic collision?

How does the kinetic energy of particles vary as a function of temperature?

Use the kinetic-molecular theory to explain the compression and expansion of gases.

List the three basic assumptions of the kinetic-molecular theory.

Describe the common properties of gases.

Compare diffusion and effusion. Explain the relationship between the rates of these processes and the molar mass of a gas.

Baking Explain why the baking instructions on a box of cake mix are different for high and low elevations. Would you expect to have a longer or a shorter cooking time at a high elevation?

What is the molar mass of a gas that takes three times longer to effuse than helium?

What is the ratio of effusion rates of krypton and neon at the same temperature and pressure?

Calculate the molar mass of a gas that diffuses three times faster than oxygen under similar conditions.

What is the partial pressure of water vapor in an air sample when the total pressure is 1.00 atm, the partial pressure of nitrogen is 0.79 atm, the partial pressure of oxygen is 0.20 atm, and the partial pressure of all other gases in air is 0.0044 atm?

What is the total gas pressure in a sealed flask that contains oxygen at a partial pressure of 0.41 atm and water vapor at a partial pressure of 0.58 atm?

Mountain Climbing The pressure atop the world's highest mountain, Mount Everest, is usually about 33.6 kPa. Convert the pressure to atmospheres. How does the pressure compare with the pressure at sea level?

High Altitude The atmospheric pressure in Denver, Colorado, is usually about 84.0 \(\mathrm{kP}\) a. What is this pres- sure in atm and torr units?

At an ocean depth of \(76.2 \mathrm{m},\) the pressure is about 8.4 \(\mathrm{atm} .\) Convert the pressure to \(\mathrm{mm} \mathrm{Hg}\) and kPa units.

Explain the difference between a temporary dipole and a permanent dipole.

Why are dispersion forces weaker than dipole-dipole forces?

Explain why hydrogen bonds are stronger than most dipole-dipole forces.

Compare intramolecular and intermolecular forces.

Hypothesize why long, nonpolar molecules would interact more strongly with one another than spherical nonpolar molecules of similar composition.