# Lecture_1 - CHM2330 Kinetic Theory of Gases 1 Molecules in...

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CHM2330 – Kinetic Theory of Gases 1 Molecules in Motion (Chapter 21 (8 th ed.) or Chapter 20 (9 th ed.)) Objective: To describe the motion of various kinds of particles in all types of fluids We will begin by describing the motion of particles in ideal gases . The Kinetic Model of Gases (Section 20.1) Three assumptions: 1. The gas consists of molecules of mass m in ceaseless random motion 2. The size of the molecules is negligible, in the sense that their diameter is much smaller than the average distance travelled between collisions with other molecules 3. The molecules interact only through brief, infrequent, and elastic collisions Actually, there is a 0 th assumption as well: 0.

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CHM2330 – Kinetic Theory of Gases 2 Relationship between pressure and molecular speeds We will show that, from the 3 assumptions, the pressure and volume of the gas are related as follows: PV nMc = 1 3 2 where: P is the pressure ( p will be for momentum) V is the volume n is the number of moles of gas M is the molar mass of the molecules c is the root-mean-square speed of the molecules: c v = 2 1 2 / Where v is the speed of the molecules and the angular brackets denote the mean.
CHM2330 – Kinetic Theory of Gases 3 Convince yourself that the mean speed of a collection of molecules is not the same as root-mean-square speed. v (m s -1 ) v 2 340 115600 333 110889 230 52900 560 313600 450 202500 326 106276 560 313600 432 186624 652 425104 203 41209 403 162409 208 43264 490 240100 399 178006 mean 422 root-mean-square of the speeds Calculation of root-mean-square speeds. Given a list of speeds, v : 1. square each value and record these as v 2 2. take the average (mean) of these v 2 values 3. take the square root of the result

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CHM2330 – Kinetic Theory of Gases 4 Elastic collision : total translational kinetic energy of the molecules is conserved Recall p = mv where
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## This note was uploaded on 08/24/2011 for the course ENGINEERIN 1122 taught by Professor Stadnik during the Spring '11 term at University of Ottawa.

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Lecture_1 - CHM2330 Kinetic Theory of Gases 1 Molecules in...

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