Unformatted text preview: gas (KE) =N ( 1 avg A 2 NA is Avogadro's number Combine these two equations
u2 = 3RT = u rms NAm mu 2 ) 3 RT 2 1 3 N A ( mu 2 ) = RT 2 2 3RT u2 = NAm (KE)avg =
41 42 m is kg for one particle, so Nam is kg for a mole of particles. We will call it M u rms = 3RT M Where M is the molar mass in kg/mole, kg/mole, and R has the units 8.3145 J/Kmol. The velocity will be in m/s 7 Example
Calculate the root mean square velocity of carbon dioxide at 25C. Calculate the root mean square velocity of hydrogen at 25C. Calculate the root mean square velocity of chlorine at 250C. Range of velocities
The average distance a molecule travels before colliding with another is called the mean free path and is small (near 107) Temperature is an average. There are molecules of many speeds in the average. Shown on a graph called a velocity distribution
44 43 273 K
number of particles number of particles 2 2  2RT f(v) = 4 ve 2RT 3 Mv 2 273 K 2 2  2RT f(v) = 4 ve 2RT 3 Mv 2 1273 K Molecular Velocity
45 46 Molecular Velocity Velocity
Average increases as temperature increases. Spread increases as temperature increases.
Mv 2 2  2RT f(v) = 4 ve 2RT 47 48 Effusion
Passage of gas through a small hole, int...
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 Spring '08
 FREEMAN
 Mole, pH

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