Unit 8: Gas Laws

Lesson 1

Kinetic Molecular Theory and Gases

KMT operates under 5 assumptions:

1. Gas particles are in _______________________________________.

2. Particles are separated by great _________________.

3. Collisions are ___________ and___________

4. No _____________ of attraction between particles.

5. Total energy remains _____________.

Average kinetic energy is _____________ proportional to temperature!! As temp goes ________, so does kinetic energy.

Kinetic-Molecular Theory

• A gas consists of very small particles, each of which has a__________.

• A gas spreads out and takes on the _____________ of its container. The volume of the gas particles is assumed to be ____________because it is negligible compared with the total volume of the gas.

• Gas particles are in________,___________ and __________ motion. They move in _______________lines, until they bump into something.

- ____________ is a measurement of the average kinetic energy (speed) of the particles

– _______________is a measurement of the number and force of the collisions of the particles with the walls of the container

• Kinetic-Molecular Theory cont.

The collisions of gas particles with each other and with the container are totally __________.

Gas particles exert ________________________because their attractions are so weak they are assumed to be zero.

• Gas Properties Relating to the Kinetic-Molecular Theory

Diffusion ____________________________________________________________.

Effusion_____________________________________________________________.

• Graham’s Law

Molecules __________________ through holes in a rubber balloon and deflate

This occurs at a rate equal to_______________________:

• proportional to _________

• inversely proportional to ____________ ____________

Therefore, He gas effuses ________ __________than O2 at the same T.

Graham’s Law

Rate of effusion

This also applies to________________, as ___________particles diffuse more _______________.

Example:Ammonia has a molar Mass of 17.0 g/mol; hydrogen chloride has a molar mass of 36.5 g/mol. What is the ratio of their diffusion rates?

What does this mean? __________________________________________________________________________________________________________________________.

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Example on your own:Carbon Monoxide is less massive than Carbon Dioxide. How much faster will CO diffuse compared to CO2?

Dalton’s Law of Partial Pressures

Dalton’s Law:

the __________ pressure exerted by a mixture of gases is the ____________of all the ___________ _____________.

PTotal =

• Example

A mixture of oxygen, carbon dioxide and nitrogen (this mix is known as “air”) has a total pressure of 0.97 atm. What is the partial pressure of O2 if the partial pressure of N2 is 0.12 atm and CO2 is 0.70 atm?

Lesson 2 “Intermolecular Forces, Liquids, and Solids”

States of Matter

The fundamental difference between states of matter is the _____________ between particles.

• The States of Matter

The state a substance is in at a particular temperature and pressure depends on two things:

The ____________ __________________of the particles

The strength of the attractions between the particles (_________________ _________)

Gas Properties

• Assumes both the _______________ and ______________ of its container • Is ____________________• __________________ readily• __________________ within a gas occurs ______________

Liquid Properties

• Assumes the ______________ of the portion of the container it occupies• Does not ______________ to fill container• Is virtually _____________________• _________________ readily• _________________ within a liquid occurs ________________

Solid Properties

• Retains its own ______________ and ________________• Is virtually ______________________• Does not ________________• Diffusion within a ______________occurs extremely _______________

Intermolecular Forces

The attractions between molecules are not nearly as strong as the ________________________ attractions that hold compounds together. (Ionic bonds, covalent bonds, etc.)

They are, however, strong enough to control _______________ ____________________such as ____________________________________________________________________________

Different Intermolecular Forces

________________________________ interactions

_________________________bonding

__________________ _________________forces

• Dipole-Dipole Interactions

Molecules that have ______________________dipoles are attracted to each other.

The positive end of one is attracted to the ___________ end of the other and vice-versa.

These forces are only important when the molecules are ____________ to each other.

• London Dispersion Forces

While the electrons in the 1s orbital of helium would __________________________ (and, therefore, tend to stay far away from each other), it does happen that they occasionally wind up on the _______________________________________________________________.

At that instant, then, the helium atom is _____________, with an excess of _______________ on the left side and a shortage on the right side.

Another helium nearby, then, would have a dipole _______________ in it, as the electrons on the left side of helium atom 2 _____________ the electrons in the cloud on helium atom 1.

London dispersion forces, or dispersion forces, are attractions between an __________dipole and an ________________dipole.

These forces are present in ________ molecules, whether they are polar or nonpolar.

The tendency of an electron cloud to distort in this way is called ____________________.

• Hydrogen Bonding

The dipole-dipole interactions experienced when _____ is bonded to ____, ______, or ________ are unusually ______________________________.

We call these interactions____________________ ________________.

This is what makes ________________________ have so many special properties

Hydrogen bonding arises in part from the high _______________________ of nitrogen, oxygen, and fluorine.

Which are stronger?

_________________________ > ________________________>

>____________________________ (induced dipole/ induced dipole)

Intermolecular Forces Affect Many Physical Properties

The strength of the attractions between particles can greatly affect the _______________of a substance or solution.

When the rates of __________________________ and ________________________ are equal, the pressure of the gas molecules __________________ a liquid is called __________________ __________________.

• Viscosity

Resistance of a liquid to flow is called _________________.

It is related to the ease with which molecules can ______________________ each other.

Viscosity ________________ with stronger _____________________________ and ___________________ with higher _______________________.

• Surface Tension

Surface tension results from the net ______________force experienced by the molecules on the __________________ of a liquid.

Phase Changes

Require Energy Release Energy

* *

* *

* *

Remember: all ______________ changes are __________________ changes!

Phase Diagrams

Phase diagrams display the _________________ of a substance at various______________________and __________________and the places where _______________exist between phases.

The AB line is the ____________________________ interface.

It starts at the ______________________ (A), the point at which all ______________states are in equilibrium.

It ends at the ________________ _________________ (B); above this critical _____________________ and critical __________________ the liquid and vapor are ________________________ from each other.

Each point along this line is the _________________________of the substance at that pressure.

The AD line is the interface between ___________________ and _______________.

The _______________ ______________ at each pressure can be found along this line.

Below A the substance cannot exist in the ___________________state.

Along the AC line the _________________ and _______________ phases are in equilibrium; the ___________________ __________ at each pressure is along this line.

Phase Diagram of Water

Note the high ______________ __________________ and ______________ _________________. These are due to the _______________ van der Waals forces between water molecules.

Phase Diagram of Carbon Dioxide

Carbon dioxide cannot exist in the ________________ state at pressures below 5.11 atm; CO2 __________________ at normal pressures.

Solids

We can think of solids as falling into two groups:

Crystalline—____________________________________________.

Amorphous—___________________________________________.

Lesson 3 “Gas Laws”

Real Gases

An _____________gas adheres to the Kinetic Theory exactly in all situations.

_________gases deviate from ideal behavior at ____________ pressures and ________ temperatures.

When the pressure is __________, it becomes more difficult to ___________ a gas because the particles actually have a ____________ of their own.

When the temperature is ____________, gas particles slow down and attractions between them become _____________________ as they clump together and form _____________.

Gas law terms:

n = ____________of gas particles

V = ______________ (of the container)

T = _______________ (must be in ___________________)

P = _________________

Temperature

______________ is the only temperature scale that measures absolute ___________ of particles.

All temperatures in gas law problems need to be in ____________________.

Pressure

1 atm =____________kPa= _____________torr=___________mmHg

1atm is the normal atmospheric pressure at _________ ___________

Pressure changes with _____________

Air pressure is measured with a _________________.

Standard Temperature and Pressure (STP)

Standard temperature =Standard pressure =

Pressure, Volume, & Temperature

Boyle’s Law

__________________and __________________are __________________ proportional if the temperature remains constant

Charles’ Law

____________________ and _____________________ are _________________ proportional if pressure remains constant. Temperature must be in _____________.

Gay-Lussac’s Law

___________________ and _____________________ are _____________ proportional if volume remains constant. Temperature must be in ________________.

Avogadro’s Law

For a gas at constant __________________ and ___________________, the _______________ is directly proportional to the ______________________________ of gas (at low pressures).

V = volume of the gas n = number of moles of gas

Avogadro’s Principle: At STP, ____________ gas is equal to ________________.

Combined Gas Law

Temperature must be in _____________. Cross out any _____________.

Sample Problem

At conditions of 785 torr of pressure and 15.0 oC temperature, a gas occupies a volume of 45.5 mL. What will be the volume of the same gas at 745 torr and 30.0oC?

Example

On a cold morning (10.0 oC) a group of hot-air balloonists start filling their balloon with air, using a large fan. After the balloon is three-fourths filled, they turn on the propane burner to heat the air. At what Celsius temperature will the air completely fill the envelope to its maximum capacity of 1700. m3?

Ideal Gas Law

R is the __________________ ________ ______________. An “R” value is picked based upon the unit being used to measure_________________________.

(R = 0.08206 atm L/mol K)(R = 8.314 kPa L/mol K)(R = 62.4 mmHg L/mol K)

Example

How many moles of a gas at 100oC does it take to fill a 1.00-L flask to a pressure of 1.50 atm?

Example

What is the volume occupied by 9.45 g of C2H2 at STP?

Gas Stoichiometry

Only gas volumes at __________ (Avogadro’s Principle: 1 mol = 22.4 L) can be entered into a stoichiometry equation

If gas is at a different __________________ and _______________, use PV=nRT to convert ____________ to ____________ and then continue with stoichiometry

Sample Problem

3 H2 + N2 2 NH3

A chemist might commonly perform this reaction (______________ process) in a chamber at 327oC under a pressure of 900. mm Hg. How many grams of ammonia would be produced from 166.3 liters of hydrogen at the above conditions?