Third Lesson
Avogadro’s Law
By end of the lesson you will learn about following things
# Avogadro’s law
# Avogadro law’s appliance
# Three corollary from Avogadro law
# Molar volume
# Avogadro number
1.1 Introduction
After publication of Dalton’s atomic theory, explained the first four chemical combinations by Dalton atomic theory. In 1811, Johns Jacob Berzelius tried to explain the law of gaseous volume by Dalton’s atomic theory and he proposed that the same temperature and pressure and same volume of gases have equal atoms.
But it goes to opposite to atomic theory that atoms are indivisible. To solve this problem in 1811 Avogadro first told clear conception about atoms and molecules and determined the difference between atoms and molecules. He also amended Dalton’s atomic theory.
By pillaring his conception about atoms and molecules Avogadro amended the explanation of Berzelius and Avogadro explained a new law that is known to all Avogadro’s hypothesis. By different experiment it has been proved that Avogadro’s hypothesis is true. Now it is called Avogadro’s law
1.2 Avogadro’s Law
Statement: The same temperature and pressure and same volume of gases (simple and compound) have equal molecules.
Suppose there have four gas matters resuectively nitrogen, hydrogen, oxygen, carbon dioxide in the same volume temperature and pressure. If any way you can prove than Nitrogen have X molecules, the other gases hydrogen, oxygen, carbon dioxide will have X molecules. But their natures, mass, molecular structure are different.
1.3 Three corollary of Avogadro’s low
(1) With out inert gas other simple gas’s molecules have two atoms.
(2) Any gas’s molecular mass is double of its vapour density.
(3) In the same temperature and pressure all gas’s molar volume are equal and it is 22.4 litters in the standard pressure and temperature.
1.4 Vapour Density
Vapour density is called the ratio of any volume of any gas and the same volume of hydrogen gas in the same temperature and pressure.
1.5 Avogadro Number
It is being that in the same temperature and pressure all gas’s molar volume is equal. Again the same temperature and pressure and same volume of gases (simple and compound) have equal molecules. So there have equal number molecules in 1 mole of all gas. This number is called Avogadro number and it is 6.02 X 1023. So N= 6.02 X 1023.
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