Ch. 10

The ideal gas law allows us to find one of the variables if we know the other __

3

Simple Gas Laws (3)

Boyle's Law, Charles' Law, and Avogadro's Law

•Robert Boyle (1627-1691) and Robert Hooke used a J-tube to measure the volume of a sample of gas at different pressures. •They trapped a sample of air in the J-tube and added mercury to increase the pressure on the gas. -They observed an inverse relationship between volume and pressure. •Hence, an increase in one causes a decrease in the other.

Boyle's law----volume and pressure

•states that the total pressure of a gas mixture is the sum of the partial pressures. •According to kinetic molecular theory, the particles have negligible size and they do not interact. -Particles of different masses have the same average kinetic energy at a given temperature. •Because the average kinetic energy is the same, the total pressure of the collisions is the same.

Dalton's Law

__ is another van der Waals constant and is different for every gas because the molecules of each gas have different strengths of attraction

a

If the lines are extrapolated back to a volume of 0, they all show the same temperature, −273.15 °C = 0 K, called

absolute zero

the number of gas particles in a given volume decreases with increasing ___. hence, pressure decreases with __ altitude

altitude, increasing

•Investigates volume and amount (mole) relationship

avogadro's law

•states that the volume of a gas is directly proportional to the number of gas molecules. •Increasing the number of gas molecules causes more of them to hit the wall at the same time. •To keep the pressure constant, the volume must then increase.

avogadro's law

•Volume is directly proportional to the number of gas molecules when pressure and temperature are held constant. -More gas molecules = larger volume •Equal volumes of gases contain equal numbers of molecules. -The gas doesn't matter.

avogadro's law--- volume and moles have a direct relationship

__ is called a van der Waals constant and is different for every gas because the molecules of each gas are of different sizes

b

•Investigates pressure and volume relationship

boyle's law

•states that the volume of a gas is inversely proportional to the pressure.

boyle's law

•Investigates volume and temperature relationship

charles's law

•When the temperature of a gas sample increases, the gas particles move faster.

charles's law

•says that the volume of a gas is directly proportional to the absolute temperature. -According to kinetic molecular theory, when we increase the temperature of a gas, the average speed—and thus the average kinetic energy—of the particles increases. •The greater volume spreads the collisions out over a greater surface area so that the pressure is unchanged.

charles's law

•The volume of a fixed amount of gas at a constant pressure increases linearly with increasing temperature in kelvins. -Volume and temperature have a direct relationship •If the volume of a gas increases with increasing temperature

charles's law---- volume and temperature have a direct relationship

Pressure of a gas is inversely proportional to its volume when temperature and the amount of gas are held ___

constant

The other gas laws are found in the ideal gas law if two variables are kept __

constant

The sum of the partial pressures of all the gases in the mixture equals the total pressure. This is known as __ __ __ ___ __

dalton's law of partial pressures

as volume increases, concentration of gas molecules __ (number of molecules does not change, but since the volume increases, the concentration goes down). This, in turn, results in fewer molecular collisions, which results in __ pressure

decreases, lower

mass/volume=

density

The process of a collection of molecules spreading out from high concentration to low concentration is called

diffusion

heavier molecules __ more slowly than lighter ones

effuse

The process by which a collection of molecules escapes through a small hole into a vacuum is called

effusion

The collision of one particle with another (or with the walls of its container) is completely __

elastic

means no exchange of energy occurs

elastic

Because the gas particles are constantly moving, they strike the sides of the container with a __. The result of many particles in a gas sample exerting forces on the surfaces around them is a constant __

force, pressur4e

-a phase of matter. -composed of particles that are moving randomly and very fast in their container(s).

gas

__ particles move in straight lines until they collide with either the container wall or another particle; then they bounce off.

gas

__ pressure is a result of the constant movement of the gas molecules and their collisions with the surfaces around them.

gas

in the concentration of gas particles, the high the concentration the __ the pressure

greater

but as the pressure increases, the molar volume of argon becomes __ __ that of an ideal gas

greater than

In 1873, Johannes van der Waals (1837-1923) modified the ideal gas equation to fit the behavior of real gases at __ pressure

high

a high density of particles results in __ pressure

high

at __ temperature, the pressure of gases is nearly identical to that of an ideal gas

high

Because real molecules take up space, the molar volume of a real gas is larger than predicted by the ideal gas law at __ __

high pressure

real gases often do not behave like ideal gases at __ pressure or __ temperature

high, low

the H in this map indicates region of __ pressure, usually associated with clear weather. the L indicates regions of __ pressure, usually associated with unstable weather

high, low

As the temperature of a gas sample increases, the velocity distribution of the molecules shifts toward __ velocity

higher

at __ pressures, the argon atoms themselves occupy a significant portion of the gas volume, making the actual volume greater than that predicted by the ideal gas law

higher

At low pressures, the molar volume of argon is nearly identical to that of an __ __

ideal gas

__ __ laws assume -no attractions between gas molecules. -gas molecules do not take up space. •Based on the kinetic molecular theory •At low temperatures and high pressures, these assumptions are not valid.

ideal gas

One of the methods chemists use to determine the molar mass of an unknown substance is to heat a weighed sample until it becomes a gas; measure the temperature, pressure, and volume; and use the __ __ __

ideal gas law

PV=nRT -->

ideal gas law

the __ __ law relationship discussed so far can be combined into a single law that encompasses all of them

ideal gas law

as temperature increases, the average velocity __

increases

as you raise the temperature of the gas, the average speed of the particles __

increases

mean free path decreases as pressure __

increases

The partial pressure from the ideal gas law can be determined by assuming that each gas component acts ___

independently

gases behave ___

independently

means there is an exchange of energy

inelastic

It reveals a curve that shows that the PV/RT ratio for a real gas is generally lower than ideal for "low" pressures—meaning that the most important factor is the __ __

intermolecular attractions

Van der Waals modified the ideal gas equation to account for the __ ___

intermolecular attractions

The average kinetic energy of the gas particles is directly proportional to the __ temperature

kelvin

the simplest model for the behavior of gases is the __ __ __

kinetic molecular theory

•In this theory, a gas is modeled as a collection of particles (either molecules or atoms, depending on the gas) in constant motion.

kinetic molecular theory

-Collisions of gas particles with each other and/or surfaces are said to be elastic—no exchange of energy occurs. -If an exchange of energy between particles and/or surfaces were to happen, then the collisions would be referred to as inelastic.

kinetic theory of gases

a low density of particles results in __ pressure

low

at __ temperatures, the pressure of gases is less than that of an ideal gas

lower

in the number of gas particles in a given volume, the lower the force per unit areas the __ the pressure

lower

The pressure of a gas trapped in a container can be measured with an instrument called a

manometer

•A competition is established between the pressures of the atmosphere and the gas. -The difference in the liquid levels is a measure of the difference in pressure between the gas and the atmosphere

manometer

___ are U-shaped tubes partially filled with a liquid that are connected to the gas sample on one side and open to the air on the other.

manometers

Average kinetic energy of the gas molecules depends on the average __ and __

mass and velocity

the average distance a molecule travels between collisions is called the _ __ __

mean free path

Density is directly proportional to

molar mass

The volume of one mole of gas at STP is called the __ __

molar volume

the volume occupied by one mole of a substance is its __ __ at STP (T=273 K or 0 °C and P = 1atm).

molar volume

The number of moles of a component in a mixture divided by the total number of moles in the mixture is the ___ ___

mole fraction

It reveals a curve that shows that the PV/RT ratio for a real gas is generally higher than ideal for "high" pressures—meaning that the most important factor is the __ __

molecular volume

Van der Waals modified the ideal gas equation to account for the __ __

molecular volume

The pressure due to any individual component in a gas mixture is its __ __

partial pressure

the pressure of a single gas in a mixture of gases is called its __ __

partial pressure

Molecular collisions are ________.

pressure

force/area=

pressure

is the force exerted per unit area by gas molecules as they strike the surfaces around them.

pressure

variation in ___ in Earth's atmosphere creates wind, and changes in pressure help us to predict weather.

pressure

4 basic properties of a gas:

pressure (P), volume (V), temperature (T), and amount in moles (n)

•Expand to completely fill their container •Take the shape of their container •Low density -Much less dense than solid or liquid state •Compressible •Mixtures of gases are always homogeneous fluid

properties of gases

many gas samples are not __ but are mixtures of gases

pure

to have same average kinetic energy, heavier molecules must have a __ average speed

slower

decreasing the volume forces the molecules into a __ space. gas particles collide with the surface more often, __ the pressure

smaller, increasing

not all gas particles are moving at the same __

speed

•Because the volume of a gas varies with pressure and temperature, chemists have agreed on a set of conditions with which to report our measurements so that comparison is easy. These are called __ __

standard conditions (STP)

a gaseous atom or molecule exerts a force when it collides with a __ and other gaseous ___.

surface, particles

In reactions involving gaseous reactants or products, the quantity of a gas is often specified in terms of its volume at a given __ and ___

temperature and pressure

1mmHg= 1 __ 760 mmHg= 1 ___ 760 torr= 1 __

torr, atm, atm

the partial pressure of the water vapor, called the __ __, depends only on the temperature

vapor pressure

the molecular __ makes the real volume larger than the ideal gas law would predict

volume

The pressure of a gas depends on several factors: -Number of gas particles in a given ___ -___ of the container -___ ___ of the gas particles

volume, volume, average speed