Chapter 9. Properties of Gases and the Kinetic Molecular Theory

Slides:



Advertisements
Similar presentations
GASES! AP Chapter 10. Characteristics of Gases Substances that are gases at room temperature tend to be molecular substances with low molecular masses.
Advertisements

Daniel L. Reger Scott R. Goode David W. Ball Chapter 6 The Gaseous State.
Chemistry AP/IB Dr. Cortes
Gases Chapter 12 pp General properties & kinetic theory Gases are made up of particles that have (relatively) large amounts of energy. A gas.
Properties of Gases Important properties of a Gas Quantity n = moles
The Behavior of Gases AW Chapter 10, section 1 and Chapter 12.
Unit 5: Gases and Gas Laws. Kinetic Molecular Theory  Particles of matter are ALWAYS in motion  Volume of individual particles is  zero.  Collisions.
Chapter 10 Gases. A Gas -Uniformly fills any container. -Mixes completely with any other gas -Exerts pressure on its surroundings.
Gases Courtesy of nearingzero.net.
Chapter 5: Gases Renee Y. Becker Valencia Community College CHM
A Gas -Uniformly fills any container. -Mixes completely with any other gas -Exerts pressure on its surroundings.
Chapter 10; Gases. Elements that exist as gases at 25 0 C and 1 atmosphere.
Prentice Hall © 2003Chapter 10 Chapter 10 Gases CHEMISTRY The Central Science 9th Edition David P. White.
Chapter 121 Gases. 2 Characteristics of Gases -Expand to fill a volume (expandability) -Compressible -Readily forms homogeneous mixtures with other gases.
Chapter 09Slide 1 Gases: Their Properties & Behavior 9.
Ch. 10 Gases. Properties Expand to fill their container Highly compressible Molecules are far apart.
Gases Chapter 5. Elements that exist as gases at 25 0 C and 1 atmosphere 5.1.
Chapter 5: The Gaseous State Chemistry 1061: Principles of Chemistry I Andy Aspaas, Instructor.
Ideal Gas Law PV = nRT re-arrange n V = P RT n = molar mass (g/mol) mol gas= mass gas (g) mass of sample V x molar mass = P RT = density mass V density.
Gases Unit 6. Kinetic Molecular Theory  Kinetic energy is the energy an object has due to its motion.  Faster object moves = higher kinetic energy 
Chapter 101 Gases. 2 Homework: 10.12, 10.28, 10.42, 10.48, 10.54, 10.66,
Prentice Hall © 2003Chapter 10 Chapter 10 Gases CHEMISTRY The Central Science 9th Edition.
Unit 5: Gases and Gas Laws
CHEMISTRY The Central Science 9th Edition
Gas Laws.
Gases.
Gases.
Gases Courtesy of nearingzero.net.
St. Charles Community College
Gas Laws.
Chapter 2 Gases COURSE NAME: CHEMISTRY 101 COURSE CODE:
PowerPoint Lecture Presentation by J
To understand the Ideal Gas Law and use it in calculations
principles and modern applications
Gases Chapter 5.
Copyright©2000 by Houghton Mifflin Company. All rights reserved.
James F. Kirby Quinnipiac University Hamden, CT
Gas Laws Chapter 5.
Quinnipiac University
Gases Chapter 5 Become familiar with the definition and measurement of gas pressure. Learn the gas law and ideal gas equation. Understand the concept of.
Quinnipiac University
WARM UP Continued from Friday: Give three possible ways that this can (The paint thinner can) got deformed. Hint: It was NOT crushed by physical means,
Gas Laws Chapter 10 CHEM140 February 2, 2005.
Quinnipiac University
Chapter 10 Gases.
Gases Chapter 5 Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.
Chapter 12 Properties Of Gases.
Quinnipiac University
Chapter 13 Kinetic Theory (Kinetikos- “Moving”)
Quinnipiac University
Gases Chapter 5.
Quinnipiac University
Gases Chapter 5 Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.
Chapter 5.
Calculating Gas Density
St. Charles Community College
Quinnipiac University
Chapter10 Gases.
Lecture Presentation Chapter 10 Gases.
Quinnipiac University
AP Chem Today: Gas Behavior and Gas Laws Review
Kinetic Molecular Theory of Gases
Quinnipiac University
Gas Laws Chapter 10 CHEM140 February 2, 2005.
Ideal Gas Law PV = nRT re-arrange n = P V RT n = mol gas
Gases Chapter 5 Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.
Quinnipiac University
Copyright©2000 by Houghton Mifflin Company. All rights reserved.
Gases Chapter 10.
Gases.
Presentation transcript:

Chapter 9. Properties of Gases and the Kinetic Molecular Theory Gas Mixtures: Partial Pressures Pressure of a Gas The Ideal Gas Law Kinetic Molecular Theory Maxwell-Boltzmann Velocity Distribution Real Gases Department of Chemistry, KAIST 1 1

An Overview of the Physical States of Matter The Distinction of Gases from Liquids and Solids 1. Gas volume changes greatly with pressure. 2. Gas volume changes greatly with temperature. 3. Gases have relatively low viscosity. 4. Most gases have relatively low densities under normal conditions. 5. Gases are miscible.

The three states of matter

9.1 Pressure of a Gas: Barometric Principles 1643, Torricelli Force necessary to suspend the barometric fluids comes from the pressure of the atmosphere

r = m/V independent of A !

at the same P, rHghHg = rH2OhH2O Can you calculate how long the water tube would be ?? 1 atm (standard atmosphere): 760 mmHg (0 oC, dry air, sea level) 760 Torr (independent of temperature) 101,325 Nm-2 (Pa) - SI unit 1,013,250 dyne cm-2 14.70 lb in-2

Effect of atmospheric pressure on objects at the Earth’s surface.

9.2 The Ideal Gas Law Boyle’s Law Charles’s Law V a 1 P n and T are fixed V x P = constant V = constant / P Charles’s Law V a T P and n are fixed V T = constant V = constant x T

Boyle’s Law

Department of Chemistry, KAIST Boyle’s Law Department of Chemistry, KAIST

Charles’ Law relationship between volume and temperature of a gas (at constant moles and Pressure).

Boyle’s Law Charles’s Law V a 1 P n and T are fixed V x P = constant V = constant / P Charles’s Law V a T P and n are fixed V T = constant V = constant x T Gay-Lussac showed that Boyle’s law continues to hold for different T, and Charles’ law for different P PV T = constant

Gay-Lussac’s experiment & Avogadro’s Explanation 1 volume hydrogen + 1 volume of chlorine  2 volumes of hydrogen chloride Avogadro: suggesting that 1) equal volumes of any gas contain equal numbers of gas molecules 2) gaseous hydrogen and chlorine are present as diatomic molecules Avogadro’s Law V a n P, T are fixed V n = constant N NA n =

combine PV T = constant & V n = constant we get Ideal Gas Law (equation of state)

Standard temperature and pressure (STP): T = 273.15 K (0 oC), P = 1 atm

Standard molar volume Equation 9.14

9.3 Gas Mixtures: Dalton’s Law of Partial Pressures Department of Chemistry, KAIST

Mixtures of Gases Dalton’s Law of Partial Pressures P1 = n1RT / V Gases mix homogeneously in any proportions Each gas in a mixture behaves as if it were the only gas present Dalton’s Law of Partial Pressures P1 = n1RT / V P2 = n2RT / V, … Ptotal = P1 + P2 + P3 + ... P1= c1 x Ptotal where c1 is the mole fraction c1 = n1 n1 + n2 + n3 +... = n1 ntotal PO2 = (0.209)(760 Torr) = 159 Torr

9.4 The Kinetic Molecular Theory Maxwell’s idea; molecules are in constant motion (random and chaotic) molecule’s coordinate is fixed at a fixed position ~ equal to the vector distance Translational kinetic energy = (1/2)mv2 (Cartesian velocity components) Probability of molecules for v ~ v+dv = 4 πv2dv

In a container of edge length L Consider one molecule

Now consider all N molecules

When this is compared to Molar kinetic energy Average energy per molecule kB = R/N Boltzmann’s constant absolute Temp is the measure of molecular motion !!

Apparatus for studying molecular velocity distribution

Maxwell-Boltzmann Distribution of Molecular Velocity Average value of energy or velocity characterizes the group average value is derived from a distribution of values

Department of Chemistry, KAIST Velocity distribution function as Temp increases, peak velocity is shifted to higher values 2) distribution is broadened Department of Chemistry, KAIST

Fraction of molecules with speeds in a given interval Interval: a to b approximation for small x

most probable molecular speed The distribution of speeds of three different gases at the same temperature The distribution of speeds for nitrogen gas molecules at three different temperatures most probable molecular speed

 ū = most probable molecular speed Average speed 8RT ∏M  ū = root-mean-square (rms) speed

8RT ∏M  The path traveled by a single gas molecule: ū =

Wall collision rate: - Zwall = ¼ (N/V) v A Molecular collision rate: - Zmol = 2 (N/V) v d2 The path traveled by a single gas molecule: Mean free path: -  = v/Zmol = 1/[2 (N/V)d2]

 M2 M1 NH4Cl  NH3 17 g/mol HCl 36 g/mol Gas diffusion is the gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties. M2 M1  r1 r2 r = flux of molecules along a concentration gradient = NH4Cl Effusion is the escape of gas through a pin hole. Effusion rate is inversely proportional to M.  NH3 17 g/mol HCl 36 g/mol

A molecular description of Boyle’s Law

A molecular description of Dalton’s law of partial pressures.

A molecular description of Charles’s Law

A molecular description of Avogadro’s Law

9.5 The Behavior of Real Gases The behavior of several real gases with increasing external pressure

The effect of intermolecular attractions on measured gas pressure Pideal = P + a(n/V)2 (P: actual pressure) actual pressure is smaller than the ideal pressure

Effect of excluded volume The effect of molecular volume on measured gas volume Effect of excluded volume Videal = V - nb actual volume is greater than the ideal volume

van der Waals Constants for Some Common Gases van der Waals equation for n moles of a real gas adjusts P up adjusts V down Gas a atm*L2 mol2 b L mol 0.034 0.211 1.35 2.32 4.19 0.244 1.39 1.36 6.49 3.59 2.25 4.17 5.46 He Ne Ar Kr Xe H2 N2 O2 Cl2 CO2 CH4 NH3 H2O 0.0237 0.0171 0.0322 0.0398 0.0511 0.0266 0.0391 0.0318 0.0562 0.0427 0.0428 0.0371 0.0305 See Example 9.5

Virial Equation of State B= B(T) 2nd viral coeff. C=C(T), … B= b-a/RT if for van der Waals gas (prove) B=0 at the Boyle temp