CHM135H1 Lecture Notes - Lecture 9: Kinetic Theory Of Gases, Molar Mass, Btg Pactual
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26 Sep 2018
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CHM135 – LECTURE 9: Liquids, Solids and Phase Changes
September 24, 2018 (Relevant Reading – Chemistry 7ed McMurray/Fay/Robinson Chapter 11.1-11.4 and
11.6-11.9)
Review – The Molecular View: Kinetic Molecular Theory
- gas made of tiny particles (atoms or molecules) moving randomly
- Volume of particle very small compared to size of container. (most of gas empty space)
- Particles aren’t attracted or repelled by each other
- Particle collisions are elastic (no energy lost through friction)
o No energy is lost during collisions, so total kinetic energy in container remains constant
- Kinetic energy increases with temperature in Kelvin. KE =
- Within a gas sample, different particles of gas have different amounts of kinetic energy
- Within a sample of gas, there’s a distribution of speed
- KE =
; M = molar mass
1)Which speed distribution belongs to the gas with
the highest molecular mass? Assuming temperature
is the same → A, because increased molar mass results
in decreased speed
2) Which speed distribution belongs to the gas with
the highest temperature? Assuming gas is the same
→ C, because increased temperature results in an
increase in speed
(diagram taken from Lecture 7 powerpoint, slide 11)
3) A 1.98L vessel contains 215 g (4.89 mol) of CO2 at 299K. Calculate the ideal gas pressure and the
van der Waals gas pressure, where a is 3.59
and b is 0.0427
. Compare to the actual
pressure of 44.8 atm
Pideal → PV = nRT, P =
Pvan der Waals →
Pactual = 44.8 atm; the closest value was given by the van der Waals equation