Chem Test: Gases

How man kPa, torr, and mm Hg are in 1.00 atm?

101.3 kPa 760 torr 760 mm Hg

True or false: raising the temperature of an enclosed gas causes its pressure to decrease

False

True or false: when a sealed container of gas is opened, gas will flow from the region of lower pressure to the region of higher pressure

False

True or false: when the temperature of a sample of steam increased from 100 degrees Celsius to 200 degrees celsius, the average kinetic energy of its particles doubles

False, it has to double in Kelvin, not celsius

True or false: heavier molecules effuse and diffuse faster

False, lighter molecules effuse and diffuse faster

When doing a gas law problem, what is the first thing you must do?

KELVIN SCALE!!!!!!

Charles's law may be written at constant pressure if the temperature is measure on what scale?

Kelvin

Gay-Lussac's law may be written if the volume is held constant and if the temperatures are measured on what scale?

Kelvin

The average kinetic energy of a collection of gas particles is directly proportional to the _________ temperature scale

Kelvin

What theory explains the behavior of gases with respect to conditions such as temperature and pressure?

Kinetic theory

List three basic assumptions of the kinetic theory about the properties of gases

No attractive or repulsive forces Volume of individual particles is zero Perfectly elastic collisions

Standard pressure

Normal atmospheric pressure at sea level Is equal to 1.00 atm, 760 torr (mm Hg), 101.3 kPa

When you know the volume occupied by one mole of gas at standard temperature and pressure, what constant may be evaluated?

Number of moles

In addition to pressure, temperature, and volume, what fourth variable must be considered when analyzing the behavior of a gas in a system?

Number of moles (n)

Ideal gas law #2

PV = mRT/M

Properties of an ideal gas

Particles have no volume No attractive forces

List the name, the symbol, and a common unit Florence the four variables that are generally used to describe the characteristics of a gas

Pressure (P) in kPa or atm Volume (V) in L Temperature (T) in kelvin Numbers of moles (n)

List four everyday items that rely on the behavior of gases to operate properly

Scuba diving equipment Pressure cooker Aerosol cans Most types of tire

Van der Waals equation

Takes the deviations between ideal gases and real gases into account

R =

0.08206 L*atm/K*moles

Mole fraction

A ratio of number of moles of a certain component of a mixture to number of moles total in mixture X1 = n1/ntotal

Ideal gas

A hypothetical gas that obeys the gas laws exactly over all ranges of pressure and temperature Do not exist b/c gases have both volume and attractive forces, but it makes the math easier and gives a very close approximation

Circle the letter next to each sentence that correctly describes how gases behave when the temperature increases. A. The average kinetic energy of the gas particles increases as the particles absorb thermal energy B. Faster-moving particles impact the walls of their container with more energy, exerting greater pressure C. When the average kinetic energy of enclosed gas particles doubles, temperature doubles and pressure is cut in half

A, B

Circle the letter of each sentence that is true about the relationship between the volume and the pressure of an enclosed gas held at a constant temperature A. When the reassure increases, the volume decreases B. When the pressure decreases, the volume increases C. When the pressure increases, the volume increases D. When the pressure decreases, the volume decreases

A, B

Circle the letter next to each sentence that is true concerning the compressibility of gases A. The large relative distances between gas particles means that there is considerable empty space between them B. The assumption that gas particles are far apart explains gas compressibility C. Compressibility is a measure of how much the volume of matter decreases under pressure D. Energy is released by a gas when it is compressed

A, B, C

The temperature at which average kinetic energy of gas particles theoretically is zero is called ____________

Absolute zero

Ideal gas law

Describes the relationship between the amount of gas and its temperature, pressure, and volume It's equation provides a mathematical relationship between the temperature, pressure, mole, and volume of a gas PV = nRT where R = ideal gas law constant

What is an inverse relationship for two variables?

As one increases, the other decreases

What does it mean to say that two variables are directly proportional?

As one increases, the other increases too and the ratio stays the same

If you notice that a sealed bag of potato chips bulges when placed near a sunny window, what can you hypothesize about the relationship between the temperature and pressure of an enclosed gas?

As temperature increases, pressure increases

Boyles law

At a constant temperature, gas pressure and volume are inversely related (as one goes up the other goes down) P1V1 = P2V2

___________ law states that for a given mass of gas at a constant temperature, the volume of the gas varies inversely with pressure

Boyle's

What do you notice about the product of pressure times volume at constant temperature? What gas law does this illustrate?

Boyle's Law

Assume that pressure, temperature, and volume inside the container are known. What general law can be used to calculate the number of moles of gas inside the container?

Combined gas law

Combined gas law

Deals with the situation where only the number of molecules stays constant P1V1/T1 = P2V2/T2

The tendency of gas molecules to move from areas of higher concentration to areas of lower concentration is called _____________

Diffusion

Is the number of moles in a sample of gas directly proportional or inversely proportional to the number of particles of gas in the sample?

Directly

How are the average kinetic energy of gas particles and their Kelvin temperature related?

Directly proportional

Gay-Lussac's Law states that the pressure of a gas is...

Directly proportional to the Kelvin temperature scale in the volume is held constant

What is Avogadro's hypothesis?

Equal volumes of gases at the same temperature and pressure contain equal numbers of particles

Avogadro's hypothesis

Equal volumes of gases at the same temperature and pressure contain equal numbers of particles Saying that two rooms of the same size could be filled with the same number of objects, whether they are marbles or baseballs

Dalton's law of partial pressure

For a mixture of gases, the total reassure is the sume of the pressures each gas would exert if it were alone Ptotal = P1 + P2 + P3 ... The sum of n(RT/V)

To meet the assumptions of ___________ gases, gases must behave in an ideal way

Ideal

What can happen if too much air is pumped into a tire?

It can burst/pop b/c there is too much kinetic energy and not enough volume

How do conditions change inside a tire when you pump it with a tire pump?

It puts more molecules into the tire and therefore increases the pressure

Density

Mass divided by volume D = m/v so D = MP/RT

Diffusion

Molecules moving from areas of high concentration to low concentration

Explain why it is dangerous to throw aerosol cans into a fire

Pressure inside the can will increase greatly (b/c of temperature increase from fire) so the high pressure can make the can burst

When the volume is reduced by one half, what happens to the pressure?

Pressure is doubled

Graham's law

States that the rate of effusion of a gas in inversely proportional to the square root of its molar mass r1/r2 = √M1/√M2

Pressure

The amount of force applied to an area P = F/A

What happens when the spray button on an aerosol spray can is pressed?

The button creates an opening between the gas in can and the atmosphere outside. Gas rushes out from the higher pressure of the can towards the lower pressure outside

Difference between real gas and ideal gas

The effect of intermolecular attractions reduces the actual pressure exerted by the gas particle with the wall of a container Less forceful collisions due to its attraction to its neighboring, thus pressure of real gas is less than an ideal gas Molecules do take up space

How does an automobile air bag protect the crash dummy from being broken as a result of impact?

The gases used to inflate the airbag are compressible and able to absorbed a considerable amount of energy

Real gases behave like ideal gases when...

The molecules are far apart The molecules don't take up as big a percentage of the space We can ignore their volume This is at low pressure Molecules are moving fast = high temperature Collisions are harder and faster Molecules are not next to each other very long Attractive forces can;t play a role

What is Graham's law of effusion?

The rate of effusion of a gas is inversely proportional to the square root of its molar mass

Effusion

The rate of escape of a gas through a pinhole into an evacuated space

Gay-Lussac's Law

The temperature and pressure of a gas are directly related and constant volume P1/T1 = P2/T2

Charles's Law

The volume of a gas is directly proportional to the KELVIN scale if the pressure is held constant V1/T1 = V2/T2

Atmospheric pressure

The weight of aire per unit of area

Partial pressure

This equation allows you to calculate the partial pressure of a gas if you know the gases' mole fraction and the total pressure P1 = X1Ptotal

True or false: Charles's law states that when the pressure of a fixed mass of gas is held constant, the volume of the gas is directly proportional to its Kelvin temperature

True

True or false: a single mathematical expression involving pressure, temperature, and volume can represent the gas laws of Boyle, Charles, and Gay-Lussac if one or another of these quantities is held constant

True

kinetic theory of gases

the constant motion of particles in a gas allows a gas to fill a container of any shape or size Gases consist of hard, spherical particles The individual volume is considered to be insignificant b/c it's so small Large empty space between particles Easily compressed and expanded No attractive or repulsive forces (not actually true, but it's so tiny we just assume there are none) Collisions between gas particles are perfectly elastic Move rapidly in constant motion

What is Dalton's law of partial pressure?

Σn(RT/V)