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The Gas Laws:

Objectives:

    1.    Explain the relationships described by Boyle's law, Charles's law and Avagadro's law.

Key Terms:

    absolute zero    molar volume    partial pressure

Notes (13-3)

The Kinetic Molecular Theory opened the door for the explanation of the relationships between gas molecules, volume and pressure.  The simple assumptions that were stated in that theory paved the way for the gas laws that we use today.  All of the gas laws are based on the following 4 variables:

P - pressure
V - volume
n - number of moles
T - temperature

Boyle's Law - Volume & Pressure

Boyle stated that the pressure and volume of a sample of gas are inversely proportional to each other.

                                            P1V1 = P2V2

Constants: T & n

Sample problem:  If a gas occupies 1L at 1atm, what will the pressure of the gas be if the volume is raised to 10L?

                    equation:                        1(atm) x 1L = ___ x 10L

                    answer:                            0.1atm

Boyle's law relates the pressure and volume of an ideal gas. Pressure times volume equals a constant.

(www.grc.nasa.gov/WWW/K-12/ airplane/Images/boyle.gif)

Charles' Law - Temperature & Volume

Charles stated that at constant pressure, the volume of a gas is directly proportional to the absolute pressure.  Application of Charles' law led to the discovery of absolute zero (theoretical point where the motion of matter ceases).

                                        V1/T1 =  V2/T2 

Constants: P & n

Sample problem:  If a gas occupies 1L at 300K, what will the temperature of the gas be if the volume is raised to 10L?

                    equation:                        1L / 300K = 10L / ___

                    answer:                            3000K

Computer Drawing of a gas confined in a blue jar with a graph to the right.

(www.grc.nasa.gov/.../Animation/ gaslab/Images/chvlmp.gif)

Avogadro's Law: Amount & Volume

Avogadro stated that equal volumes of gas at the same temperature and pressure contained the same number of particles.  Remember the volume of any gas at STP is 22.4L

                                        P1V1/T1 =  P2V2/T2 

                                         V1/n1 =  V2/n2

Constants: P,T, & n = 22.4L @ STP

Sample problem:  If a gas occupies 22.4L at 273K and 1atm, what will the volume of the gas be if the pressure is raised to 10atm?

                    equation:                       (1atm x 22.4L )/ 273K = (10atm x ___ )/ 273K

                    answer:                            2.24L

(www.riverdeep.net/.../che_gat_images/ Full_800049.gif)

Daltons's Law: Partial pressures

Dalton stated that the sum of the partial pressures of all of the gases in a mixture is equal to the total pressure of the gas mixture.  

                                        PTotal = P1 + P2 + P3 + ...

Constants: T, V, & n = 22.4L @ STP

Sample problem:  If the atmospheric pressure at sea level is 760mmHg, what are the partial pressures of the constituent gases if N

                    equation:                      

                    answer:                         

                                                            O2

                                                          

                                                                                                                                760mmHg

(www.riverdeep.net/.../che_gat_images/ Full_800050.gif)

 

 

 

 

 

 

Last modified: February 25, 2003