Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Chemistry FIFTH EDITION Chapter 5 Gases
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 What is the gas composition of the Earth’s atmosphere? Two dominate gases? Other gases?
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4
5 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. 6 Atmospheric Pressure = Weight of the Air Results from the mass of the air being pulled toward the center of the earth by GRAVITY. Measured using a ______________? barometer.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Figure 5.2 A Torricellian Barometer At sea level = 760 mm Hg At elevation of 9600 feet = 520 mm Hg
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8
9 Figure 5.3 A Simple Manometer Instrument used to measure pressure of gas in a Container.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 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
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Pressure Units 1 atmosphere (atm) = 760 mm Hg = 760 torr = 101,325 Pa = inch Hg = 14.7 lb/ in 2 (psi)
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 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. 13 Figure 5.4 A J-Tube Similar to the One Used by Boyle
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure 5.5 Plotting Boyle’s Data from Table 5.1 (a) P versus V forms hyperbola (b) V versus 1/P straight line with slope = k and y-intercept = 0
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Figure 5.6 A Plot of PV versus P for Several Gases at Pressures Below 1 ATM These are actually only small changes. Changes are much more significant at much higher pressures.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 A gas that strictly obeys Boyle’s Law is called an ideal gas.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Boyle’s Law is a good approximation at pressure close to 1 atmosphere. Deviations are small. Read Sample Exercise 5.3.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Figure 5.7 A Plot of PV Versus P for 1 mol of Ammonia
Charles’ Law At constant pressure and mass of gas: VTVT V = b * T where b is a proportionality constant Vol. increases linearly with Temp. (at constant P).
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 5.8 Plots of V Versus T (ºC) for Several Gases
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 This point is 0 Kelvin!! K = C + 273
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Figure 5.9 Plots of V Versus T ( in Kelvin) Volume =0 at T = 0 K
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 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. 24 Charles’s Law
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Avogadro’s Law Equal Volumes of Gases at the Same Temperature & Pressure contain the Same Number of “Particles.”
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Figure 5.10 Balloons Holding 1.0 L of Gas at 25º C and 1 atm. Each balloon contains mole of gas or 2.5 x molecules.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 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. 28 Problem Solving Combined Gas Law: P 1 V 1 = P 2 V 2 T 1 T 2 Temperature must be in Kelvin.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 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 An Ideal Gas is a hypothetical substance. Ideal Gas Law is an empirical equation.
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 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. 31 Homework Don’t forget about your Homework?