Ideal gas Assumptions 1.Particles that form the gas have no volume and consist of single atoms....
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Transcript of Ideal gas Assumptions 1.Particles that form the gas have no volume and consist of single atoms....
Ideal gas
• Assumptions1. Particles that form the gas have no volume
and consist of single atoms.2. Intermolecular interactions are vanishingly
small.
Ideal gas
Equations of statePV=NkTP= pressureV= volume N=number of particles of gask= Boltzmann Constant= 1.38x10-23J/KK=Kelvin temperature
Ideal gas
Equations of statePV=nRTP= pressureV= volumen=number of moles of gasR= Universal Gas Constant= K=Kelvin temperature
8.31J
mol K
Ideal gas
Avogadro’s number
236.022 10A
moleculesN x
mol
Ideal gas
Relationship between Avogadro’s number, Universal Gas constant, and Boltzmann constant.
AR k N
Kinetic –molecular theory
1. Many molecules are in a container and they behave like point particles.(No volume)
2. The molecules move around randomly, and obey Newton’s laws.
3. The only interactions that the molecules undergo are elastic collisions with each other and the walls of the container.
Kinetic –molecular theory
Pressure is a result of the molecules colliding with the walls of the container. As the number of molecules or thir average speed increases, the pressure increases.
Kinetic –molecular theory
Results of kinetic-molecular theory.
21 3
2 2
Kelvin temperature
avav
K mv kT
T
Kinetic –molecular theory
Results of kinetic-molecular theory.
3 3
Kelvin temperature
m= the mass of one molecule
M= the mass of one mole of molecules
rms
kT RTv
m MT
Kinetic –molecular theory
Internal energy of an ideal monatomic gas..
3 3
2 2Kelvin temperature
N= number of molecules
n= number of moles
U NkT nRT
T
Kinetic –molecular theory
Other gas laws – the amount of gas does not change
1 1 2 2
1 2
1 2
1 1 2 2
1 2
Boyle's Law - applies at constant temperature
P V =P V
Charles' Law - applies at constant pressure
Combined Gas Law
V V
T T
PV PV
T T
Laws of Thermodynamics
The first Law of Termodynamics –If U is the internal energy of a system, than DU=Q-W.
If Q>0 System gains heat
If Q<0 System loses heat
If W>0 Work is done by the system
If W<0 Work is done on the system
Laws of Thermodynamics
The first Law of Thermodynamics –If U is the internal energy of a system, than DU=Q-W
Table 18-1Signs of Q and W
Q positive System gains heat
Q negative System loses heat
W positive Work done by system
W negative Work done on system
Figure 18-1The Internal Energy of a System
Figure 18-2Work and Internal Energy
Laws of Thermodynamics
At constant pressure, the work done by or on a system is
W=PΔV
The area under a PV curve represents work. If a process occurs at a constant volume, the work done during the process is 0.
Figure 18-5A Constant-Pressure Process
Example 18-2Work Area
Laws of Thermodynamics
Isothermal processes – these are processes that take place at a constant temperature.
PV=constant
Figure 18-8Isotherms on a PV Plot
Laws of Thermodynamics
Adiabatic processes – these are processes that take place without heat entering or leaving the system.
During an adiabatic process Q=0 and
U Q W
U Q W W
Figure 18-9An Isothermal Expansion
Figure 18-10aAn Adiabatic Process
Figure 18-10bAn Adiabatic Process
Conceptual Checkpoint 18-2 Page 578Which is the adiabatic curve?
Figure 18-14A Comparison Between Isotherms and Adiabats