Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 A Gas 4 Uniformly fills any container. 4 Mixes completely with any other gas 4 Exerts pressure on its surroundings.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Pressure 4 is equal to force/unit area 4 SI units = Newton/meter 2 = 1 Pascal (Pa) 4 1 standard atmosphere = 101,325 Pa 4 1 standard atmosphere = 1 atm = 760 mm Hg = 760 torr

Measuring Pressure The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17 th century. The device was called a “barometer” Baro = weight Meter = measure

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Figure 5.2 A Torricellian Barometer

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Figu re 5.3 A Simple Manometer

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Figure 5.4 A J-Tube Similar to the One Used by Boyle

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Pressure Conversion Practice

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Boyle’s Law *

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Boyle’s Law * Pressure  Volume = Constant (T = constant) P 1 V 1 = P 2 V 2 (T = constant) V  1/P (T = constant) ( * Holds precisely only at very low pressures.)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Boyle’s Law *

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Figure 5.5 Plotting Boyle’s Data from Table 5.1

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 A gas that strictly obeys Boyle’s Law is called an ideal gas.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Figure 5.6 A Plot of PV versus P for Several Gases at Pressures Below 1 ATM

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure 5.7 A Plot of PV Versus P for 1 mol of Ammonia

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Charles’s Law

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Charles’s Law The volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin. V = bT (P = constant) b = a proportionality constant

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Charles’s Law

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Figure 5.8 Plots of V Versus T (ºC) for Several Gases

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Figure 5.9 Plots of V Versus T

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Charles’s Law

Converting Celsius to Kelvin Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins =  C °C = Kelvins - 273

Temperature Conversion Practice

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Avogadro’s Law For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas (at low pressures). V = an a = proportionality constant V = volume of the gas n = number of moles of gas

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Figure 5.10 Balloons Holding 1.0 L of Gas at 25º C and 1 atm V/n = a Where a is a constant So, what is the value of a at 25°C and 1 atm? (What is its value at STP) V/n is Molar Volume

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Figure 5.11 A Mole of Any Gas Occupies a Volume of Approximately 22.4 L at STP

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Ideal Gas Law 4 An equation of state for a gas. 4 “state” is the condition of the gas at a given time. PV = nRT

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Ideal Gas Law PV = nRT R = proportionality constant = L atm   mol  P = pressure in atm V = volume in liters n = moles T = temperature in Kelvins Holds closely at P < 1 atm

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 Standard Temperature and Pressure “STP” P = 1 atmosphere T =  C The molar volume of an ideal gas is liters at STP

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Dalton’s Law of Partial Pressures For a mixture of gases in a container, P Total = P 1 + P 2 + P

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Figure 5.12 Partial Pressure of Each Gas in a Mixture

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 Figure 5.13 The Production of Oxygen by Thermal Decomposition of KCIO 3

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Ideal Gas Law Manipulation Combined Gas Equation 1 – first state 2 – second state Molar Volume of a Gas Density of a Gas m – mass D – density M – molar mass

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Kinetic Molecular Theory 1.Volume of individual particles is  zero. 2.Collisions of particles with container walls cause pressure exerted by gas. 3.Particles exert no forces on each other. 4.Average kinetic energy  Kelvin temperature of a gas.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 The Meaning of Temperature Kelvin temperature is an index of the random motions of gas particles (higher T means greater motion.)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 Effusion: describes the passage of gas into an evacuated chamber. Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Effusion: Diffusion:

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 Real Gases Must correct ideal gas behavior when at high pressure (smaller volume) and low temperature (attractive forces become important).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Real Gases corrected pressure corrected volume P ideal V ideal