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The Kinetic-Molecular Theory of Matter. Objective 2.05. Ideal Gases. An imaginary gas that perfectly fits all the assumptions about kinetic molecular theory Kinetic Molecular Theory of Gases (KMT) explains the properties of gases. Kinetic-Molecular Theory of Gases.
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The Kinetic-Molecular Theory of Matter Objective 2.05
Ideal Gases • An imaginary gas that perfectly fits all the assumptions about kinetic molecular theory • Kinetic Molecular Theory of Gases (KMT) • explains the properties of gases
Kinetic-Molecular Theory of Gases • Assumptions about Ideal Gases • particles are spread far apart • mostly empty space • Collisions are elastic collisions • Particles are in continuous, random motion • no forces of attraction or repulsion • average kinetic-energy = temperature
However……. • Real Gases • Do not follow KMT completely • But we can use the KMT to describe them • How they differ: • Occupy space • Particles ARE attracted to each other (to some degree) • Nonpolar gases deviate less than polar gases
Nature of gases explained by KMT • Expansion • Fluidity • Low Density • Compressibility • Diffusion
Units of pressure • Mm of Hg • Torr • Atmospheres (atm) • Kilopascals (kPa) • Pressure Unit Conversions • 1 atm = 760 mmHg = 760 torr = 101.3 kPa
Units of Temperature • Celsius (˚C) • Kelvin (K) K = ˚C + 273
Standard temperature and pressure(STP) • 1 atm…OR • 760 mm Hg • 760 torr • 101.3 kPa • 273 K (0° C)
The Gas Laws • Combined Gas Law P1V1 = P2V2 T1 T2 Used to determine pressure, temperature or volume of a gas
Examples of Gas Problems using Combined Gas Law • Pg. 315 Sample Problem 10-2 • Pg. 318 Sample Problem 10-3 • Pg. 320 Sample Problem 10-4 • Pg. 321 Sample Problem 10-5 • Remember T must be in Kelvin! • Remember P units must be all the same! • Whichever unit is constant cancels out!!!
The Gas Laws • Boyles Law: • Charles Law: • Gay Lussac’s Law
Ideal Gas Law • Mathematical relationship among pressure, volume, temperature, and the number of moles of a gas • PV=nRT (given on Reference Guide) • Pressure (P) • Volume (V) • Number of moles (n) • Ideal gas constant (get from table on sheets) • Temperature (T)
Examples of Ideal Gas Problems • Pg. 342 Sample Problem 11-3 • Pg. 343 Sample Problem 11-4 • Pg. 344 Sample Problems 11-5
Dalton’s Law of Partial Pressures • The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases • PT=P1+P2+P3+… (given on reference guide) • Also…for gas collected over water • PT = Pgas + PH2O
Example of Partial Pressures Problem • Pg. 324 Sample Problem 10-6 • To get water pressure use • Water Vapor Pressure Table Appendix A pg 899
Avogadro’s Law for Gases • Gases of the same volume, at the same temp and pressure, have the same number of molecules! • n/V = n/V • A mole ratio in an equation can become a VOLUME ratio when all compounds are gases
Example of Avogadro’s Law H2(g) + Cl2(g) 2HCl (g) Mole Ratio: 1 mol:1mol:2mol Volume Ratio: 1L : 1L :2L
Molar Volume of A Gas • At STP 1 mole of any gas = 22.4 L New Branch on Mole Map