Chemistry Chapter 7

Calculate the volume of each substance at STP. (A)4.2 mol Ar (B)3.5 g CO2 (C)2.1 g N2

(A) 94 L (B) 1.8 L (C) 1.7 L

How many moles of helium are contained in each volume at STP: (a) 5.0 L; (b) 11.2 L; (c) 50.0 mL?

(a) 0.22 mol (b) 0.500 mol (c) 0.00223 mol

Use the following values to answer each part. The specific heat of water is 1.00 cal/(g · °C); the heat of fusion of water is 79.7 cal/g; and the heat of vaporization of water is 540 cal/g. (a)How much energy (in calories) is needed to melt 45 g of ice at 0.0 °C and warm it to 55 °C? (b)How much energy (in calories) is released when 45 g of water at 55 °C is cooled to 0.0 °C, and frozen to solid ice at 0.0 °C? (c)How much energy (in kilocalories) is released when 35 g of steam at 100. °C is condensed to water, the water is cooled to 0.0 °C, and the water is frozen to solid ice at 0.0 °C?

(a) 6,100 cal (b) 6,100 cal (c) 25 kcal

Classify each solid as amorphous, ionic, molecular, network, or metallic. (a)KI (b)CO2 (c)bronze, an alloy of Cu and Sn (d)diamond (e)the plastic polyethylene

(a) ionic (b) molecular (c) metallic (d) network (e) amorphous

Indicate whether heat is absorbed or released in each process. (a)melting 100 g of ice (b)freezing 25 g of water (c)condensing 20 g of steam (d)vaporizing 30 g of water

(a),(d) absorbed (b),(c) released

How many moles of gas are contained in a human breath that occupies 0.45 L and has a pressure of 747 mm Hg at 37 °C?

0.017 mol

How many moles of air are present in the lungs if they occupy a volume of 5.0 L at 37 °C and 740 mm Hg? How many molecules of air does this correspond to?

0.19 mol 1.1x10^23 molecules

STP- Standard conditions of temperature and pressure

1 atm (760mmHg) for pressure and 273k (0 degree C) for temperature

The partial pressure of N2 in the air is 593 mm Hg at 1 atm. What is the partial pressure of N2 in a bubble of air a scuba diver breathes when he is 66 ft below the surface of the water where the pressure is 3.00 atm?

1,780 mmHg

An autoclave is a pressurized container used to sterilize medical equipment by heating it to a high temperature under pressure. If an autoclave containing steam at 100. °C and 1.0 atm pressure is then heated to 150. °C, what is the pressure inside it?

1.1 atm

If a balloon containing 2.2 L of gas at 25 °C is cooled to −78 °C, what is its new volume?

1.4 L

If you pack a bag of potato chips for a snack on a plane ride, the bag appears to have inflated when you take it out to open. Explain why this occurs. If the initial volume of air in the bag was 250 mL at 760 mm Hg, and the plane is pressurized at 650 mm Hg, what is the final volume of the bag?

290 mL The gases inside the bad had a volume of 250 mL at 760 mmHg and take up a greater volume at the reduced pressure of 650 mmHg

If a scuba diver releases a 10.-mL air bubble below the surface where the pressure is 3.5 atm, what is the volume (in mL) of the bubble when it rises to the surface and the pressure is 1.0 atm?

35 mL

Air pressure on the top of Mauna Loa, a 13,000-ft mountain in Hawaii, is 460 mm Hg. What are the partial pressures of O2 and N2, which compose 21% and 78% of the atmosphere, respectively?

97 mmHg for O2 360 mmHg for N2

Which of the following samples has the higher temperature? (a)100. g of liquid water at 16.0 °C that absorbs 200. cal of heat (b)50.0 g of liquid water at 16.0 °C that absorbs 350. J of heat

A

Barometer

A device for measuring atmospheric pressure

Combined Gas Law

A gas law that relates pressure, volume, and temperature. For a constant number of moles, the product of pressure and volume divided by temperature is constant

Ideal gas Law

A gas law that relates the pressure, volume, temperature, and number of moles of a gas in a single equation PV=nRT, where R is a constant

Gay- Lussac's Law

A gas law that states for a fixed amount of gas at constant volume, the pressure of the gas is proportional to its Kelvin Temperature

Charles Law

A gas law that states that for a fixed amount of gas as constant pressure, the volume of the gas is proportional to its Kelvin Temperaure

Avogadro's law

A gas law that states that the volume of a gas is proportional to the number of moles present when the pressure and the temperature are constant

Boyle's Law

A gas that relates pressure and volume, Boyle's law states that for a fixed amount of gas at constant temperature, the pressure and volume of the gas are inversly related

Heating Curve

A graph that shows how the temperature of a substance changes as heat is added

Cooling Curve

A graph that shows how the temperature of a substance changes as heat is removed

What changes are depicted on heating and cooling curves?

A heating curve shows how the temperature of a substance changes as heat is added. Diagonal lines show the temperature increase of a single phase. Horizontal lines correspond to phase changes—solid to liquid or liquid to gas. A cooling curve shows how the temperature of a substance changes as heat is removed. Diagonal lines show the temperature decrease of a single phase. Horizontal lines correspond to phase changes—gas to liquid or liquid to solid.

metallic solid

A lattice of metal cations surrounded by a cloud of electrons that move freely

Dalton's Law

A law that states that the total pressure (Ptotal) of a gas mixture is equal to the sum of the partial pressures of its component gasses

Viscosity

A measure of a fluids resistance to flow freely

Surface Tension

A measure of the resistance of a liquid to spread out

Describe the energy changes that accompany changes of state.

A phase change converts one state to another. Energy is absorbed when a more organized state is converted to a less organized state. Thus, energy is absorbed when a solid melts to form a liquid, or when a liquid vaporizes to form a gas. Energy is released when a less organized state is converted to a more organized state. Thus, energy is released when a gas condenses to form a liquid, or a liquid freezes to form a solid. The heat of fusion is the energy needed to melt 1 g of a substance, whereas the heat of vaporization is the energy needed to vaporize 1 g of a substance.

Sublimation

A phase change in which the solid phase enters the gas phase without phasing through the liquid state

Gas Laws

A series of laws that relates the Pressure, Volume, and Temperature of a gas

Network Solid

A solid composed of a vast number of atoms covalently bonded together, forming sheets or 3-D arrays

Molecular Solid

A solid composed of individual molecules arranged regularly

Ionic Solid

A solid composed of oppositely charged ions in a regular arrangment

Crystalline Solid

A solid with a regular arrangement of particles- atoms, molecules, ions- with a repeating structure.

Amorphous Solid

A solid with no regular arrangement of its particles

Kinetic-Molecular Theory

A theory that describes the fundamental characteristics of gas particles

Atmosphere

A unit used to measure pressure 1 atm= 760 mmHg

Millimeters of Mercury

A unit used to measure pressure abbreviated as mmHg and also called "torr"

A balloon is filled with helium at sea level. What happens to the volume of the balloon in each instance? Explain each answer. A)The balloon floats to a higher altitude. B)The balloon is placed in a bath of liquid nitrogen at −196 °C. C)The balloon is placed inside a hyperbaric chamber at a pressure of 2.5 atm. D)The balloon is heated inside a microwave.

A) Volume increases as outside atmospheric pressure decreases B) Volume decreases at the lower temperature C) Volume decreasese as external pressure increases D) Volume increases as temperature increases

Convert each quantity to the indicated unit. A)2.8 atm to psi B)520 mm Hg to atm C)20.0 atm to torr D)100. mm Hg to Pa

A)41 psi B)0.68 atm C)15,200 torr D)13,300 Pa

Hydrogen Bonding

An attractive intermolecular force that occurs when a hydrogen atom bondes to O,N,F is electrostatically attracted to an O,N,F atom in another molecule

Describe the relationship between the volume and number of moles of a gas.

Avogadro's law states that when temperature and pressure are held constant, the volume of a gas is proportional to its number of moles. One mole of any gas has the same volume, the standard molar volume of 22.4 L, at 1 atm and 273 K (STP).

What are gas laws and how are they used to describe the relationship between the pressure, volume, and temperature of a gas?

Because gas particles are far apart and behave independently, a set of gas laws describes the behavior of all gases regardless of their identity. Three gas laws—Boyle's law, Charles's law, and Gay-Lussac's law—describe the relationship between the pressure, volume, and temperature of a gas. These gas laws are summarized in "Key Equations—The Gas Laws" on page 254. For a constant amount of gas, the following relationships exist. The pressure and volume of a gas are inversely related, so increasing the pressure decreases the volume at constant temperature. The volume of a gas is proportional to its Kelvin temperature, so increasing the temperature increases the volume at constant pressure. The pressure of a gas is proportional to its Kelvin temperature, so increasing the temperature increases the pressure at constant volume.

Given the following vapor pressures at 20 °C, arrange the compounds in order of increasing boiling point: butane, 1,650 mm Hg; acetaldehyde, 740 mm Hg; Freon-113, 284 mm Hg.

Butane, acetaldehyde, Freon-113

What is Dalton's law and how is it used to relate partial pressures and the total pressure of a gas mixture?

Dalton's law states that the total pressure of a gas mixture is the sum of the partial pressures of its component gases. The partial pressure is the pressure exerted by each component of a mixture.

Vapor

Gas molecules formed from the evaporation of a liquid

What types of intermolecular forces exist and how do they determine a compound's boiling point and melting point?

Intermolecular forces are the forces of attraction between molecules. Three types of intermolecular forces exist in covalent compounds. London dispersion forces are due to momentary changes in electron density in a molecule. Dipole-dipole interactions are due to permanent dipoles. Hydrogen bonding, the strongest intermolecular force, results when a H atom bonded to an O, N, or F, is attracted to an O, N, or F atom in another molecule. The stronger the intermolecular forces, the higher the boiling point and melting point of a compound

Which sample contains more moles: 2.0 L of O2 at 273 K and 500. mm Hg, or 1.5 L of N2 at 298 K and 650 mm Hg? Which sample has more mass?

O2 has more moles and more mass

what units are used to measure it?

Pressure is measured by a barometer and recorded in atmospheres (atm), millimeters of mercury (mm Hg), or pounds per square inch (psi). 1 atm = 760 mm Hg = 14.7 psi.

What is pressure?

Pressure is the force per unit area. The pressure of a gas is the force exerted when gas particles strike a surface.

Describe the features of different types of solids

Solids can be amorphous or crystalline. An amorphous solid has no regular arrangement of particles. A crystalline solid has a regular arrangement of particles in a repeating pattern. There are four types of crystalline solids. Ionic solids are composed of ions. Molecular solids are composed of individual molecules. Network solids are composed of vast repeating arrays of covalently bonded atoms in a regular three-dimensional arrangement. Metallic solids are composed of metal cations with a cloud of delocalized electrons.

What is specific heat?

Specific heat is the amount of energy needed to raise the temperature of 1 g of a substance by 1 °C. Specific heat is used as a conversion factor to calculate how much heat a known mass of a substance absorbs or how much its temperature changes.

Heat of fussion

The amount of energy needed to melt one gram of a substance

Heat of Vaporazation

The amount of energy needed to vaporize one gram of a substance

Specific Heat

The amount of heat energy needed to raise the temperature of 1g of a substance by 1 degree C

Inter-molecular forces

The attractive forces that exist between molecules

Dipole-Dipole interactions

The attractive intermolecular forces between the permanent dipoles of two polar molecules

Universal gas constant

The constant, R, that equals the Product of the Pressure and volume of a gas divided by the product of the number of moles and Kelvin Temperature R=PV/nT

Deposition

The conversion of a gas directly to a solid

Condensation

The conversion of a gas to a liquid

Vaporization

The conversion of a liquid to a gas

Freezing

The conversion of a liquid to a solid

Melting

The conversion of a solid to a liquid

Evaporation

The conversion of liquid molecules to gas molecules

Pressure

The forces (f) exerted per unit area (A) symbolized by P

What is the ideal gas law?

The ideal gas law is an equation that relates the pressure (P), volume (V), temperature (T), and number of moles (n) of a gas; PV = nRT, where R is the universal gas constant. The ideal gas law can be used to calculate any one of the four variables, as long as the other three variables are known.

A gas (4.0 g) occupies 11.2 L at 2 atm and 273 K. What is the molar mass of the gas? What is the identity of the gas?

The molar mass is 4g/mol and the gas is helium

Vapor Pressure

The pressure above a liquid exerted by gas molecules in equilibrium with the liquid phase

Partial Pressure

The pressure exerted by one component of a mixture of gases

Boiling Point

The temperature at which a liquid is converted to the gas phase

Normal Boiling Point

The temperature at which the vapor pressure above a liquid equals 760 mmHg

Melting Point

The temperature of a solid is converted to the liquid phase

Standard Molar Volume

The volume of one mole of any gas at STP- 22.4L

Describe three features of the liquid state—vapor pressure, viscosity, and surface tension.

Vapor pressure is the pressure exerted by gas molecules in equilibrium with the liquid phase. Vapor pressure increases with increasing temperature. The higher the vapor pressure at a given temperature, the lower the boiling point of a compound. Viscosity measures a liquid's resistance to flow. More viscous compounds tend to have stronger intermolecular forces or they have high molecular weights. Surface tension measures a liquid's resistance to spreading out. The stronger the intermolecular forces, the higher the surface tension.

Explain why cooling a full glass water bottle to −10 °C causes the bottle to crack.

Water is one of the few substance that expands as it enters the solid phase. This causes the bottle to crack when the water occupies a larger volume as it freezes

London Dispersion Forces

very weak intermolecular interactions due to the momentary changes in electron density in a molecule