The law of gas diffusion and the liquefaction of gas

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4 The law of gas diffusion

British physicist Graham proposed that the diffusion rate u of a gas at the same temperature and pressure is inversely proportional to the square root of its density ρ
.

This is the law of gas diffusion

by

Get

Substituting it into the gas diffusion law formula, we get

That is, the gas diffusion rate at the same temperature and pressure is inversely proportional to the square root of the molar mass

[Example 1-2] The diffusion rate of gas A is about twice that of methane gas.
Determine what kind of gas A is by calculation

Solutions of methane gas molar mass · mol 16G ^-1
.

The molar mass of gas A is

Judging by the molar mass of gas A, the gas is He
.

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5 Liquefaction of gas

Generally, the method of cooling or pressurizing is used to liquefy the gas

The maximum temperature at which a gas can be liquefied by pressurization is called the critical temperature of the gas, represented by T _c ; the minimum pressure required to liquefy the gas when the critical temperature is reached is called the critical pressure of the gas, represented by p _c ; Above the critical temperature and critical pressure 1mol some critical volume occupied by the gas volume of the gas is referred to by V _C expressed
.
The state when the gas is at the critical temperature and critical pressure at the same time is called the critical state

Critical state is a special form of existence of matter.
At this time, gas and liquid are of the same nature, regardless of state, and often have unconventional properties
.
People use the special properties of the critical state to synthesize some substances that are difficult to synthesize under normal circumstances, and extract and separate some substances that are difficult to extract under normal circumstances

Related links: The state of actual gas and the law of partial pressure of gas