Chapter 7 Homework

When a sample of gas is compressed from 6.0 L to 2.0 L at a constant temperature, the pressure of the gas triples.

True

When the volume of a sample of gas is doubled and the Kelvin temperature is doubled, the pressure of a sample remains constant.

True

Whether a substance exists as a gas, liquid, or solid depends on the balance between the kinetic energy of its particles and the strength of the interactions between the particles.

True

Surface tension measures which of the following?

A liquid's resistance to spreading out

Which molecule(s) exhibit London dispersion forces?

All of the molecules exhibit London dispersion forces.

Three of the four phase changes below are endothermic. Which phase change is NOT endothermic?

Condensation

A scuba diver typically begins a dive with a compressed air tank at 2,350 psi. What is this pressure expressed in units of Pa?

1.62 × 10^7 Pa

What volume does 7.50 × 1020 molecules of O2 occupy at STP?

0.0279 L

What volume does 7.50 × 10^20 molecules of O2 occupy at STP?

0.0279 L

A patient's systolic pressure is measured as 128 mm Hg. What is this pressure in units of atm?

0.168 atm

How many moles are contained in 5.33 L of O2 at standard temperature and pressure?

0.238 mol of O2

A sample of neon gas has a volume of 5.0 mL at a pressure of 1.50 atm. What is the pressure exerted by the gas if the volume is increased to 30.0 mL, at constant temperature?

0.25 atm

How many moles of gas are contained in a scuba diver's 12.6-L tank filled with 3422 psi of air at 25 °C?

120. moles

A scuba diver typically begins a dive with a compressed air tank at 2,350 psi. What is this pressure expressed in units of mm Hg?

1.21 × 105 mm Hg

An aerosol can has a pressure of 1.86 atm. What is this pressure expressed in units of mm Hg?

1410 mm Hg

Air pressure at the bottom of Death Valley, at 282 ft below sea level, is 776 mm Hg. What are the partial pressures of O2 and N2, which compose 21% and 78% of the atmosphere, respectively?

160 mm Hg O2 and 610 mm Hg N2

A 54.2 L sample of gas at 115 K is heated to 345 K, at constant pressure. What volume does the gas now occupy?

163 L

Atmospheric pressure in interstellar space is approximately 1 × 10^-17 torr at a temperature of -173 °C. How many gas molecules are present in 25,000 L of interstellar space (about the volume of a bedroom)?

2 × 10^7 molecules

A weather balloon contains 233 L of helium at 22 °C and 760. mm Hg. What is the volume of the balloon when it ascends to an altitude where the temperature is -54 °C and 511 mm Hg?

257 L

A sample of gas contains four gases (He, Ne, Ar, and Xe) with the following partial pressures: He (43 mm Hg), Ar (835 mm Hg), and Xe (111 mm Hg). If the total pressure in the container is 1355 mm Hg, what is the partial pressure of Ne in the sample?

366 mm Hg

What is the volume of 62.3 g of nitrogen gas at STP?

49.8 L

A gas cylinder containing 6.38 mol of neon has a pressure of 491 mm Hg at 295 K. If 3.22 mol of helium is added to this cylinder, at constant temperature and volume, what will be the pressure in the cylinder?

739 mm Hg

The normal boiling point of a liquid is the temperature at which its vapor pressure equals which of the following?

760 mm Hg

A sample of gas contains four gases with the following partial pressures: He (113 mm Hg), Ne (184 mm Hg), Ar (35 mm Hg), and Xe (445 mm Hg). What is the total pressure of the sample?

777 mm Hg

A birthday balloon contains helium at a pressure of 815 torr. What is this pressure expressed in units of mm Hg?

815 mm Hg

A gas cylinder containing 3.88 mol of helium has a pressure of 549 mm Hg at 298 K. If 1.22 mol of neon is added to this cylinder, at constant temperature and volume, the pressure will rise to 1750 mm Hg.

False

All solids are crystalline solids.

False

Charles's law can be used to explain the dangerous condition for scuba divers called "the bends," which is caused by the formation of nitrogen gas bubbles in the bloodstream.

False

Condensation is the opposite of sublimation.

False

Ethylene glycol is expected to be less viscous than propane.

False

Gas pressure is the result of particles of gas colliding with each other.

False

If two compounds have the same molecular formula they will have the same boiling point.

False

London dispersion forces are the strongest type of intermolecular forces.

False

STP is defined as a pressure of exactly one atmosphere and a temperature of 25 °C.

False

Some nail polish removers contain acetone. When acetone evaporates, the covalent bonds between the carbon, hydrogen, and oxygen atoms are broken.

False

The higher the vapor pressure of a compound, the higher the boiling point of the compound.

False

The size of gas particles is large compared to the space between the particles.

False

The value of the universal gas constant, R, changes as a function of temperature.

False

Two molecules of dimethyl ether, whose structure is shown below, are capable of hydrogen bonding with each other.

False

When 88.4 g of hydrogen gas is put in a 25.8-L container at 300. K, the pressure will be 83.7 atm.

False

When a sample of gas is heated from 80 °C to 160 °C at a constant pressure, the volume of the gas doubles.

False

When the pressure and temperature are held constant, the volume of a gas is inversely proportional to the number of moles present.

False

When the volume of a sample of gas is doubled and the Kelvin temperature is cut in half, the pressure of a sample remains constant.

False

Which molecule(s) exhibit hydrogen bonding?

HF

Propanol, CH3CH2CH2OH, has the structure shown below. What is the strongest type of intermolecular force that exists between two propanol molecules?

Hydrogen bonding

Which is an ionic solid?

KCl

Consider the two liquids A and B shown in closed containers. Which liquid exhibits the stronger intermolecular forces?

Liquid A

Consider the two liquids A and B shown in closed containers. Which liquid has the higher vapor pressure?

Liquid B

Butane, CH3CH2CH2CH3, has the structure shown below. What is the strongest type of intermolecular force that exists between two butane molecules?

London dispersion forces

When octane evaporates, what kind of attractive forces are overcome?

London dispersion forces between octane molecules

Which phase change below is endothermic?

Melting

Which is a network solid?

SiO2

The pressure of a gas is proportional to its Kelvin temperature at constant volume and number of moles. Therefore increasing the temperature increases the pressure.

True

At rest, the volume of air in the lungs is 615 mL at 760 mm Hg. When the volume of the lungs expands during inhalation, what happens to the pressure inside the lungs?

The pressure inside the lungs decreases, which draws air into the lungs.

An aerosol spray can with a volume of 350 mL registers a pressure of 4.5 atm at room temperature. What happens to the pressure of the gas inside the can if the can is stored outside during the winter months?

The pressure of the gas will be less than 4.5 atm.

The energy required to break up the attractions between ethylene glycol molecules is greater than the energy required to break up the attractions between propane molecules.

True

The numerical value of the universal gas constant, R, depends on its units.

True

A 22.4 g sample of O2 will occupy less than 22.4 L at STP.

True

Energy is released when a less organized state is converted to a more organized state.

True

Evaporation is an endothermic process.

True

Freeze-drying removes water from foods by the process of sublimation.

True

Gases expand to fill the volume and shape of their container because the rapidly moving particles experience negligible attractive forces for each other.

True

It requires less heat to melt a 10-g sample of water than to vaporize a 10-g sample of water.

True

London dispersion forces are also referred to as van der Waals forces.

True

London dispersion forces are exhibited by all covalent compounds.

True

NaCl has a higher melting point than sucrose (C12H22O11)

True

Polypropylene, a typical plastic, is an example of an amorphous solid.

True

Sarin, a nerve gas once used as a chemical weapon, has a melting point of -56 °C and a boiling point of 158 °C. A sample of sarin at room temperature (22 °C) exists as a liquid.

True

The stronger the intermolecular forces, the lower the vapor pressure of a substance at a given temperature.

True

Which cylinder at STP will contain the greatest mass of gas particles?

a 5.0-L cylinder of nitrogen