Chapter 5 Gases
Chapter 5 Gases
WHY?
Sketch of Modern
Balloons
WHY?
Mathematics
V/T = constant
1.00
PSI
8.00
PSI
8.00
PSI
WHY?
Mathematics
PV = constant
Mathematics
V/n = constant
•(n
= moles)
Moles
273
K
1.00
ATM
804
K
9.79
ATM
(atm)
Mathematics
P/T= constant
Mathematics
Summary
V/n = constant
V/T = constant
P/T = constant
PV = constant
Mathematics
Summary
V/nT = constant
P/T = constant
PV/nT = constant
Mathematics
PV/nT =Summary
constant
PV = nTconstant
•constant
=R
PV = nRT Ideal Gas Law
Conditions
of
Use
PV = nRT Ideal Gas Law
•P
units must be atm’s
•V
units must be liters
•T
must be in Kelvin
Gas Law Resources
Pressures equivalent to the standard 1.00 ATM
28.3 ft. H2O
29.92 in. Hg
76.0 cm Hg
760.0 mm Hg
760.0 torr
14.7 psi.
Practice
• Fill out the following chart.
• mm Hg. atm. kPa.
•
•
•
.
.
.
1215
0.714
143
bar
Gas Law Resources
Temperature - must be absolute - never negative
•
•
Temperature must be in Kelvin
K=
oC
+ 273
Practice
• Calculate the volume of 1.0 mole of
a gas at Standard Temperature and
Pressure.
Practice
• Fill out the following chart for C H
• Press. Vol. Temp. Moles Grams
4
•
•
•
1.75 L
.
.
0.895 atm
433 mm Hg
19 oC
6.0
oC
92.4 mL
1.74 bar
.
8.66 L
14.0
0.395
.
•
1.66
310 K
10
Experiment
Experiment
Experiment
4 Fe + 3 O2  2 Fe2O3
Fe + N2  NR
Interpretation
• Air contains both N and O
• Each gas has its own independent
2
2
pressure.
• “The sum of all individual gas pressures in
a gas mixture is equal to the total
pressure” DALTON
• Dalton’s Law of Partial Pressures
(go to video)
KMT
•Kinetic Molecular Theory of gases
Gases consist of very tiny particles in
continuous random motion.
Particle collisions are elastic(no energy
lost).
Particle volume is negligible.
Particle interaction is negligible.
•molecular speed causes both pressure and
volume of gases
Graham’s Law
• Often called Grahams’ Law of Diffusion - in error
• Diffusion - movement of gas down an open tube
• complex and influenced by many factors.
• Effusion - movement of gas through small holes.
• Graham’s Law of Effusion of Gases
• “At
a given temperature and pressure, gaseous
effusion rate in moles per time unit, is inversely
proportional to the square root of the molar mass
of the gases”.
• effusion rate of B
• effusion rate of A
=
 
 
Ideal vs Real
• Review KMT. Obvious non-realities.
• Some gas molecules are NOT tiny.
• Many gas collisions DO lose energy
• Gas molecules HAVE a noticeable volume
• Some molecules have SIGNIFICANT interaction.