PHYSICS 5B Lecture 5: Physics lecture 5
the ideal gas law
-never interacting
PV=nRT or PV =NKBT
-an empirical law
-n=#of moles of atoms /molecules
↳one
mole
of
anything
=6.022×1023 "
anything
''
-N= total #of atoms /molecules (can be found In periodic Table )
-R= Universal gas constant .8.315 J/mole .K
-KB
=1¥ =1.38 ×10-23
J/k
Sl P→1Pa
),V→(m3 ),T→(k)
e± Estimate the mass of the .air in abedroom
P= latm =1×105 Pa
V=4mi 4m ×3m = 50 m3
T=20°C a300k
PV .NRT
n=,P¥ =1×105/51 =2000 mol
8. 3X300
m= n.molar mass
for air 80% Nz +20%02
N:14µmol
.0:168 /MOI
.:M=0.8×2×14 +0.2 ×3.16 =29 g/mol
Mt 2000 .29 =57600 g.
=60kg
-Macroscopic description :ideal gas law
*The Kinetic Theory of gases
(amircoscopk interpretation of the thermodynamics quantities (ie p,T
,ete
.)
O→g°¥ very large #of randomly moving molecules /atoms (particles)
each particles follows The Newton 's Law Ot motion individually .
method :statistics +Newton smechanics =Statistical Mechanics
Y
q
F=velocity vector
Omt
'
V=speed scalar
x
2
For agiven particle V;
n
T:
=Vxi It Vyiy +Vz;
Z
V,
?= V×i2 +Vy ,
?+VI. 2
-In fact :gas molecules do not travel at asingle speed
(e± :some molecules reach 100 Mls at RT )
