IDEAL GAS LAW

QUICK REVIEWBoyle’s Law: P1V1= P2V2

Pressure and volume are inversely proportional

Charles Law: V1 = V2

T1 T2 Volume and temperature are directly

proportionalGay Lussac’s Law: P1 = P2

T1 T2

Pressure and volume are directly proportional

TOGETHER THE VARIABLES FORM…

THE COMBINED GAS LAW

P1V1= P2V2

T1 T2** Gaining and understanding of these laws

allows you to understand how gases behave when you change the pressure,

volume, or temperature of a gas sample.**

GASES BEHAVE THE SAME WAY.

According to the Kinetic Molecular Theory, gases:

1. Consist of a large number of particles that are far apart.

2. Undergo elastic collisions, which means, no energy is lost- kinetic energy is conserved.

3. Are in continuous rapid motion.4. Are neither attracted to or repelled by

other gas particles.5. Are dependent upon temperature for the

speed of their particles.

A real gas does not completely behave according

to the assumptions of this theory.

An ideal gas conforms to all of the the assumptions of

this theory.

IDEAL GAS LAW The ideal gas law assumes that all

gases behave perfectly and identically to the rules of the kinetic molecular theory.

It shows the relationship between pressure, volume, temperature, and the amount of gas in moles.

It can be used to find one of the four variables given the other three.

IDEAL GAS LAW FORMULA

PV= nRT

P= Pressure: The force per unit are applied to the surface of an object.

The pressure of the air molecules in this tornado can knock down numerous trees…

V= VOLUME: THE MEASUREMENT OF HOW MUCH SPACE MATTER TAKES UP.

THE VOLUME OF THIS AIR TAKES UP ENOUGH SPACE TO FILL A HOT AIR BALLOON!!!

n= Amount of gas in moles

R= Gas Constant

.0821 atm L mol

K

T= Temperature: a measure of the average kinetic energy of particles of

matter.Common Units of Temperature:

Kelvin (K): The only units that can be used when doing numerical problems with gases.

Celsius (°C): Must be converted to Kelvin before doing problems (add 273).

MORE ON RRRRRRR….

“R” is the gas constant. It uses ALL of the units that are represented in the formula by other variables.

Units in the gas constant: atm L mol K

For every problem the units of your variables have to be in the units used in the gas constant!!

PRESSURE CONVERSIONS: BACK TO DIMENSIONAL ANALYSIS

**Quick Tip: To convert from unit to unit you have to have a conversion factor.** A Conversion factor relates the unit that you start with and the unit that you want to convert too.

MORE ON PRESSURESome word problems may give you pressure

in a variety of ways.Atmospheres (atm): The average air

pressure at sea level.Millimeters of Mercury(mmHg): originates

from how pressure is measured with a barometer.

Torr: Named Italian physicist Evangelista Torricelli. The torr is exactly equal to mmHg.

KiloPascal (kPa): Another SI unit for pressure.

HERE’S THE CONNECTION…

In these amounts, all of these units are EQUAL!!!

1 atm =760 mmHg =760 torr =101.3 kPa

YOU HAVE TO MEMORIZE THESE CONVERSIONS!!!

EXAMPLE 1: CONVERT A PRESSURE OF 1.75 ATMOSPHERES TO KILOPASCALS.

EXAMPLE 2: CONVERT A PRESSURE 570 TORR TO ATMOSPHERES.

EXAMPLE: THE ATMOSPHERIC PRESSURE IN DENVER COLORADO IS .830 ATMOSPHERES. WHAT IS THE PRESSURE IN A) MMHG B)KPA

MORE GRAM TO MOLE CONVERSIONS

**Quick Tip: MOLAR MASS is the only thing that can help you convert from grams to moles!!**

O2= _______g 64g O2= _______mol

HF= ________g 40g HF= ___________mol 

CO2= __________g 88g CO2= _______mol

FREQUENTLY USED TERMS IN WORD PROBLEMS: MEMORIZE THESE!!!

Standard Temperature and Pressure: (STP)Pressure= 1 atm

Temperature= 273K or 0°C

Room Temperature: Kelvin scale= 298 K Celsius scale = 25°C

If a word problems refers to “STP” or “room temperature”, it is important for you to know these fixed values.

IDEAL GAS LAW EXAMPLE 1:

A sample of gas has a volume of 10 liters,a pressure of 1.5 atm, and a temperature of 25°C, how many moles of gas do I have?

IDEAL GAS LAW EXAMPLE 2:

If I have 3.5 moles of a gas at a pressure of 895 kPa with a volume of 50 liters, what is the temperature?