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The physical quantities that describe the gas are pressure p, volume V, temperature T and the amount of matter n
.
The unit of pressure p is Pa (Pascals, 1Pa=1N·m -2 ), the unit of volume V is m 3 (cubic meters), the unit of temperature T is K (Kelvin), and the unit of substance n is mol (mole )
1.
1.
1 Ideal gas
1.
The concept of ideal gas
Ideal gas is an idealized model abstracted on the basis of actual gas.
It is a gas that ignores the gravitational force between gas molecules and the volume occupied by gaseous molecules
.
In other words, there is no energy loss in collisions between ideal gas molecules or between molecules and walls, and the gas volume can be compressed infinitely
The real ideal gas does not actually exist.
The properties of the actual gas under the conditions of high temperature and low pressure are very similar to the ideal gas and can be approximated as an ideal gas
.
2.
Ideal gas equation of state
The relationship between the ideal gas pressure p, temperature T, volume V, and the amount of matter n is called the ideal gas equation of state
pV=nRT
In the formula, R is the molar gas constant (R=8.
314 Pa·m 3 ·mol -1 ·K -1 =8.
314J·mol -1 ·K -1 )
.
Under different conditions, the ideal gas equation of state has different expressions
.
When n is constant, it conforms to the relational expression
When n and T are constant, it conforms to Boyle's law
p 1 V 1 = p 2 V 2
When n and p are constant, it conforms to Gay-lLussac's law
When T and p are constant, it conforms to Avogadro's law
Substituting into the ideal gas equation of state, the molar mass of the gas can be found
In the formula, m is the mass of the gas; p is the density of the gas
.
[Example 1-1] At 298K and 101.
3kPa, the density of gas A is 1.
80g·dm -3
(1) The molar mass of gas A;
(2) The pressure inside the container when the closed container is heated to 400K
Solution (1) From the derived formula of the ideal gas state equation pV=nRT, get the molar mass of gas A
(2) From the ideal gas state equation pV=nRT, if n and V remain unchanged, we get
Then the pressure in the container at 400K is
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