Unit 6

Combined gas law

(P1 x V1) / T1 = (P2 x V2) / T2

At what temperature do particles theoretically have no kinetic energy?

0 K or -273.15oC

What is a pressure of 0.520 atm equal to in mm of Hg?

0.520 atm/ 760 mm Hg / 1 atm = 395 mm Hg

How many moles of n are in a flask with a volume of 250 mL at a pressure of 300.0 kPa and a temperature of 300.0 K?

250 mL = 0.25 L and R = 8.31 L kPa/ mol K; n = PV/RT = (300.0 kPa) (0.25 L) / (8.31 L kPa/ mol K) (300.0 K) = 0.030 mol

How many phases of water are in equilibrium at the triple point?

3

The vapor pressure of 10 mL of ethanol at 20oC is 5.85 kPa. What is the vapor pressure of 20 mL of ethanol at the same temperature?

5.85 kPa

Ideal gas constant

8.31 (L x kPa) / (K x mol)

Explain how pumping air into a bicycle tire increases the pressure within the tire.

Adding air increases the number of gas particles in the tire. Collisions of particles with the inside walls of the tire cause the pressure that is exerted by the enclosed gas. Therefore, increasing the number of air particles increases the number of collisions, which in turn increases the pressure within the tire.

What are some of the differences between a real gas and an ideal gas?

An ideal gas is one that follows the gas laws at all conditions of pressure and temperature. The behavior of a real gas deviates from the behavior of an ideal gas, particularly at low temperatures and high pressures. Also, kinetic theory assumes that the particles of an ideal gas have no volume and are not attracted to each other. This is not true for real gases. Real gases can be liquefied and sometimes solidified by cooling and applying pressure, but ideal gases cannot.

Explain why it takes longer to hard boil an egg at high altitudes than at sea level.

At high altitudes, atmospheric pressure is lower. Therefore, the boiling point of water is lower than at sea level. Because the highest temperature the water can reach while boiling is lower, the cooking time is increased.

ideal gas law

P x V = n x R x T

The volume of a gas is 250 mL at 340.0 kPa pressure. What will the volume be when the pressure is reduced to 50.0 kPa, assuming the temperature remains constant?

P1 V1 = P2 V2 = (250 mL) (340.0 kPa) / (50.0 kPa) = 1700 mL

How does the air pressure in a balloon change when the balloon is squeezed? Explain why this change occurs.

The air pressure increases. Squeezing reduces the enclosed volume of the balloon without changing the number of particles in the balloon. Consequently, the number of collisions between the particles and the balloon increases.

Name the basic assumptions that the kinetic theory makes about gases.

The kinetic theory is based upon the following assumptions: A gas is composed of tiny particles with an insignificant volume. Gas particles are in constant random motion. All collisions between gas particles are perfectly elastic.

The three assumptions of the kinetic theory as applied to a gas:

The particles in a gas are considered to be small, hard spheres with an insignificant volume. The motion of the particles in a gas is rapid, constant, and random. All collisions between particles in a gas are perfectly elastic

Explain why a liquid in an open container will evaporate completely over time.

The particles in a liquid have a range of energies. At any particular temperature, some particles have enough energy to overcome the attractive forces at the surface of the liquid and escape to the vapor state. As these particles escape, the temperature of the liquid would normally decrease. However, the liquid can absorb energy from the environment to maintain a constant temperature. As a result, additional particles will gain enough energy to escape the liquid. This process of escape, absorption of energy, and escape is repeated until the liquid has evaporated completely.

How does the pressure of an enclosed gas in a rigid container change when the gas is heated? Explain why this change occurs.

The pressure increases when the gas is heated because increasing the temperature of the gas increases the average kinetic energy of the particles in the gas. With an increase in average kinetic energy, there will be an increase in the number of collisions between the particles and the container walls. In addition, because the particles are moving faster, on average, the collisions will occur with greater force. Both factors, the increased frequency of collision and the increased force of the collisions, contribute to the increase in pressure.

When you place ice cubes on the table on a hot summer day, they melt and the liquid water then evaporates. What happens to dry ice (solid carbon dioxide) if it is left on the table?

The vapor pressure of dry ice exceeds atmospheric pressure at room temperature. Therefore, dry ice sublimes. The carbon dioxide changes directly from a solid state to a gaseous state.

barometer

a device used to measure atmospheric pressure

Effusion

a gas escapes through a tiny hole in its container

The conditions of pressure and temperature at which two phases exist in equilibrium are indicated on a phase diagram by

a line separating the two regions representing the phases

Compressibility

a measure of how much the volume of matter decreases under pressure

compressibility

a measure of how much the volume of matter decreases under pressure

vapor pressure

a measure of the force exerted by a gas above a liquid

crystal

a solid in which the particles are arranged in an orderly, repeating pattern

amorphous solid

a solid that lacks an ordered internal structure

Scientists inflate a weather balloon similar to the one pictured in Figure 14.13 on page 463 of your textbook. On earth, the balloon may have a volume of 2.5 x 104 L at 97.0 kPa and a temperature of 22.0oC. What would be the volume of the same balloon when the temperature drops to 10.0oC, and the pressure drops to 42.0 kPa? a. 5.5 x 104 L b. 2.6 x 104 L c. 1.2 x 104 L d. none of the above

a. 5.5 x 104 L

If the volume of a container of gas is reduced, what will happen to the pressure inside the container? a. The pressure will increase. b. The pressure will not change. c. The pressure will decrease. d. The pressure depends on the type of gas.

a. The pressure will increase.

Why does the pressure inside a container of gas increase if more gas is added to the container? a. There is an increase in the number of collisions between particles and the walls of the container. b. There is an increase in the temperature of the gas. c. There is a decrease in the volume of the gas. d. There is an increase in the force of the collisions between the particles and the walls of the container.

a. There is an increase in the number of collisions between particles and the walls of the container.

According to the kinetic theory, collisions between molecules in a gas a. are perfectly elastic. b. are inelastic. c. never occur. d. cause a loss of total kinetic energy.

a. are perfectly elastic.

How does the gas propellant move when an aerosol can is used? a. from a region of high pressure to a region of lower pressure b. from a region of high pressure to a region of equally high pressure c. from a region of low pressure to a region of higher pressure d. from a region of low pressure to a region of equally low pressure

a. from a region of high pressure to a region of lower pressure

When the Kelvin temperature of an enclosed gas doubles, the particles of the gas a. move faster. b. strike the walls of the container with less force. c. decrease in average kinetic energy. d. decrease in volume.

a. move faster.

In the kinetic theory, the particles in a gas a. move independently of each other. b. move slowly. c. are relatively close together. d. have attractive and repulsive forces.

a. move independently of each other.

The average potential energy of water molecules is greatest in a. steam at 100oC. b. liquid water at 90oC. c. liquid water at 373 K. d. ice at 0oC.

a. steam at 100oC.

___________ refers to the change of a solid directly to a vapor. a. sublimation b. evaporation c. vaporization d. vapor pressure

a. sublimation

In dry air the partial pressure of nitrogen is 79.11 kPa. a. true b. false

a. true

Keeping the amount of gas and the pressure constant while you raise the temperature will cause the volume of a gas to increase. a. true b. false

a. true

kinetic theory

all matter consists of tiny particles that are in constant motion

Dalton's Law

at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases (Ptotal = P1 + P2 + P3 ...)

What happens to the range of energies of the particles in matter when the temperature is increased? a. The range of energies becomes narrower. b. The range of energies becomes broader. c. The range of energies does not change. d. The range of energies cannot be determined.

b. The range of energies becomes broader.

A real gas differs the most from an ideal gas the most at high temperatures and low pressures. a. true b. false

b. false

Chlorine gas will effuse more quickly than ammonia gas. a. true b. false

b. false

Do gases with larger molecular (or atomic) masses behave more like ideal gases? a. true b. false

b. false

If the atmospheric pressure on Mt. Everest is one-third the atmospheric pressure at sea level, the partial pressure of oxygen on Everest is ___________. a. one-sixth its pressure at sea level b. one-third its pressure at sea level c. one-half its pressure at sea level d. equal to its pressure at sea level

b. one-third its pressure at sea level

When a gas is heated, a. all of the absorbed energy is converted to kinetic energy. b. some of the absorbed energy is converted to potential energy, and some is converted to kinetic energy. c. all of the absorbed energy is converted to potential energy. d. none of the energy is converted to kinetic energy.

b. some of the absorbed energy is converted to potential energy, and some is converted to kinetic energy.

Charles's law states that the ___________. a. pressure of a gas is inversely proportional to its temperature in kelvins b. volume of a gas is directly proportional to its temperature in kelvins c. pressure of a gas is directly proportional to its temperature in kelvins d. volume of a gas is inversely proportional to its temperature in kelvins

b. volume of a gas is directly proportional to its temperature in kelvins

Gas pressure is the result of

billions of rapidly moving particles in a gas simultaneously colliding with an object

When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to

boil

Standard conditions when working with gases are defined as a. 0 K and 101.3 kPa. b. 0 K and 1 kPa. c. 0oC and 101.3 kPa. d. 0oC and 1 kPa.

c. 0oC and 101.3 kPa.

The average speed of oxygen molecules in air is about ___________. a. 0 km/h b. 170 km/h c. 1700 km/h d. 17,000 km/h

c. 1700 km/h

If a balloon containing 3000 L of gas at 39oC and 99 kPa rises to an altitude where the pressure is 45.5 kPa and the temperature is 16oC, the volume of the balloon under these new conditions would be calculated using the following conversion factor ratios: ___________. a. 3000 L x 99 kPa x 39oC / 45.5 x 16oC b. 3000 L x 45.5 kPa x 289 K / 99 kPa x 312 K c. 3000 L x 99 kPa x 289 K / 45.5 kPa x 312 K d. 3000 L x 99 kPa x 312 K / 45.5 x 289 K

c. 3000 L x 99 kPa x 289 K / 45.5 kPa x 312 K

When the external pressure is 505 kPa, what is the vapor pressure of water at its boiling point? a. 0 kPa b. 101.3 kPa c. 505 kPa d. 1010 kPa

c. 505 kPa

sing Figure 14.15 on page 468 of your textbook, which line is most like the response of an ideal gas? a. H2 b. CH4 (at 0oC) c. CH4 (at 200oC) d. CO2

c. CH4 (at 200oC)

If energy is added to a boiling liquid, what happens to the temperature of the liquid? a. It increases. b. It decreases. c. It does not change. d. The change cannot be determined.

c. It does not change.

If the volume of a container of air is reduced by one-half, what happens to the partial pressure of oxygen within the container? a. It is reduced by one-half. b. It does not change. c. It is doubled. d. It is reduced by one-fourth.

c. It is doubled.

In a dynamic equilibrium between the liquid state and the gas state, what is true about the rate of evaporation? a. It is greater than the rate of condensation. b. It is less than the rate of condensation. c. It is equal to the rate of condensation. d. The rate of evaporation cannot be determined.

c. It is equal to the rate of condensation.

Consider an iron cube and an aluminum cube. If the two cubes were at the same temperature, how would the average kinetic energy of the particles in iron compare with the average kinetic energy of the particles in aluminum? a. The average kinetic energy of the iron particles would be greater. b. The average kinetic energy of the aluminum particles would be greater. c. There would be no difference in the average kinetic energies. d. No determination can be made based on the information given.

c. There would be no difference in the average kinetic energies.

The escape of molecules from the surface of a liquid is known as ___________. a. condensation b. boiling c. evaporation d. sublimation

c. evaporation

The average kinetic energy of the particles of a substance a. is not affected by the temperature of the substance. b. increases as the temperature of the substance is lowered. c. is directly proportional to the temperature of the substance. d. is equal to the total energy absorbed by the substance.

c. is directly proportional to the temperature of the substance.

The physical properties of liquids is determined by a. the disruptive motions of particles in a liquid only. b. the attractions among the particles only. c. the interplay between the disruptive motions of particles in a liquid and the attractions among the particles. d. either the disruptive motions of particles in a liquid or the attractions among the particles.

c. the interplay between the disruptive motions of particles in a liquid and the attractions among the particles.

The rate of effusion of which gas would be closest, at the same temperature, to Ne? a. CO2 b. N2 c. Ar d. CH4

d. CH4

Why is a gas easier to compress than a liquid or a solid? a. Its volume increases more under pressure than an equal volume of liquid does. b. Its volume increases more under pressure than an equal volume of solid does. c. The space between gas particles is much less than the space between liquid or solid particles. d. The volume of a gas's particles is small compared to the overall volume of the gas.

d. The volume of a gas's particles is small compared to the overall volume of the gas.

When the vapor pressure of a liquid is equal to the atmospheric pressure, the liquid ___________. a. has no observable changes b. boils vigorously c. evaporates d. begins to boil

d. begins to boil

At a certain temperature and pressure, 0.20 mol of carbon dioxide has a volume of 3.1 L. A 3.1 L sample of hydrogen at the same temperature and pressure___________. a. has the same mass b. contains the same number of atoms c. has a higher density d. contains the same number of molecules

d. contains the same number of molecules

In general, for a gas at a constant volume, the ___________. a. pressure of the gas is inversely proportional to its temperature in kelvins b. volume of the gas is inversely proportional to its temperature in kelvins c. volume of the gas is directly proportional to its temperature in kelvins d. pressure of the gas is directly proportional to its temperature in kelvins

d. pressure of the gas is directly proportional to its temperature in kelvins

The combined gas law relates which of the following? a. pressure and volume only b. temperature and pressure only c. volume and temperature only d. temperature, pressure, and volume

d. temperature, pressure, and volume

If the temperature is constant, as the pressure of a gas increases, the volume

decreases

The Kelvin temperature of a substance is _______________ to the average kinetic energy of the particles of the substance

directly proportional

During evaporation, only those molecules with a certain minimum kinetic energy can

escape from the surface of the liquid

Sublimation occurs in solids with vapor pressures that

exceed atmospheric pressure at or near room temperature

Gases of lower molar mass diffuse and effuse

faster than gases of higher molar mass

Boyle's Law

for a given mass of gas at constant temperature, the volume of the gas varies inversely with pressure (P1 x V1 = P2 x V2)

As the temperature of an enclosed gas increases, the volume

increases if the pressure is constant

As the temperature of a closed gas increases, the pressure

increases if the volume is constant

Real gases differ most from an ideal gas at

low temperatures and high pressures

When only the amount of gas is constant, the combined gas law describes the relationship among

pressure, volume, and temperature

diffusion

tendency of molecules to move to regions of lower concentration

Factors that affect gas pressure

the amount of gas, the volume, and the temperature

The shape of a crystal reflects

the arrangement of the particles within the solid

vaporization

the conversion of a liquid to a gas below the boiling point

kinetic energy

the energy an object has due to its motion

effusion

the escape of gas through a small hole in a container

What determines the physical properties of liquids?

the interplay between the disruptive motions of particles in a liquid and the attractions among the particles

When the pressure, volume, and temperature of a contained gas are known, you can use the ideal gas law to calculate

the number of moles of the gas

The general properties of solids reflect

the orderly arrangement of their particles and the fixed location of their particles

partial pressure

the pressure exerted by a gas in a mixture

Gay-Lussac's Law

the pressure of a gas is directly proportional to its Kelvin temperature if the volume is kept constant (P1 / T1 = P2 / T2)

atmospheric pressure

the pressure resulting from the collision of atoms and molecules with objects

Graham's Law

the rate at which a gas will effuse is inversely proportional to the square root of the gas's molar mass RateA / RateB = √ (Molar MassB / Molar Mass A)

unit cell

the smallest group of particles within a crystal that retains the shape of the crystal

Gases are easily compressed because of

the space between the particles in a gas

In a mixture of gases, the total pressure is

the sum of the partial pressure of the gases

melting point

the temperature at which a solid changes into a liquid

normal boiling point

the temperature at which the vapor pressure of a liquid is equal to 1 atmosphere

boiling point

the temperature at which the vapor pressure of a liquid is equal to the external pressure

Diffusion

the tendency of molecules to move towards areas of lower concentration until the concentration is uniform throughout

Charles's Law

the volume of a fixed mass of gas is directly proportional to its Kelvin temperature, if the pressure is kept constant (V1 / T1 = V2 / T2)

allotropes

two or more different molecular forms of an element in the same physical state

In a system at a constant vapor pressure, a dynamic equilibrium exists between the

vapor and the liquid. The system is in equilibrium because the rate of evaporation of liquid equals the rate of condensation of vapor

evaporation

vaporization at the surface of a liquid that is not boiling