# Ideal Gas Equation.ppt - RanelaghALevelPhysics by dfhdhdhdhjr

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Ideal Gas Equation/Molar &
Molecular Mass

Thermal Physics Lesson 4
Learning Objectives
Define a mole
Calculate the number of moles in a gas using
N=nNA

Perform calculations using the ideal gas equation
pV=nRT
Describe the conditions for which a real gas
behaves like an ideal gas
One mole of any gas contains
the same number of particles.
This number is called
the symbol NA. The value of
NA is 6.02 × 1023 particles per
mole.
Calculating the Number of Moles
The number of moles, n, of a gas can be can be
calculated using:-

N
n
NA
Where N is the total number of molecules
and NA is Avogadro’s constant (=6.02 × 1023)
The most significant consequence of
Avogadro's law is that the ideal gas
constant has the same value for all
gases. This means that the constant is
given by:-

V n                        p1V1 p2V2
       constant
T1n1 T2 n2
Deriving Ideal Gas Equation
1
From Boyle’s Law:               V
p
From Pressure Law:
V T
V n
Combining these three:        nT
V
p
Rewriting using the gas
constant R:                     nT    Therefore:-

 p 
V  R        pV  nRT
    
The Ideal Gas Equation
Combining the three gas
laws gives the equation:-
pV
 constant
The constant is equal to    T
nR.

Works well for gases at
low pressure and fairly
pV  nRT
high temperatures
Equation of State
Recall that each phase can exist in a variety of
states e.g. the temperature and pressure

Thus the Ideal Gas Equation of State
pV = nRT summarises the physically possible
combinations of p, V and T for n moles of the
ideal gas.

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