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Avogadro’s Hypothesis

Avogadro’s hypothesis Importance - Avogadro’s number, Molar Mass and Concept of mole

Avogadro’s law helps us identify the amount of gaseous substances present inside any closed container. This can also be named Avogadro’s hypothesis or Avogadro’s principle. This law is nothing but a simple type of experimental law of gases. This hypothesis involves the volume of gases and the quantity of a gaseous substance contained in it. This law can be considered as a precise case to determine a perfect gas law.

This particular Avogadro’s law defines that the gases will be found to have the same amounts of molecules when they are mixed at the same temperature and pressure and are presented inside a receptacle. For any given weight of the gas, the volume of the substance of the gas will be equal because they all have the same pressure and temperature and are kept constant throughout the end. So, Amedeo Avogadro has concluded that even if there are various kinds of gases kept together whose volumes are the same, then they also possess the same temperature as well as the same amount of pressure in them.

For instance, if two ideal gases such as nitrogen and hydrogen are well mixed and are kept together in equal amounts, then they consist of the same number of molecules present in them. This will happen only when they are kept at the same temperature and pressure. So, from this, we can clearly understand the ideal nature of gases.

The following is the equation for this law in a mathematical term,

We can express the entire law as,

V ∞ n

or, in other terms,

V/n= k(a constant)


V = gas volume symbol

n = gaseous substance measured as circles

k = constant defined for a specific temperature and pressure

When comparing it to the same type of element under various conditions, the following expression is obtained,

avogadros hypothesis

The above equation shows the number of moles in the gas can be enhanced in the gas volume. We can see that, when the gas mole number goes down, its volume also goes down. Hence, the size of the gas can be found independent of the entire amount of atoms or molecules in any specific volume of gas.

Avogadro’s number

It is determined as the total amount of units in one mole of any substance. This is equal for both the heavier gas like carbon dioxide and the lightest gas, hydrogen. Avogadro’s number value is 6.022*1023 which is used globally.

Importance of Avogadro’s hypothesis

His law has built an excellent relationship between how the amount of gas (n) is related to its volume (v). This law was found to be very helpful as it acted as a significant way to save a good amount of time and cash in the long run.

Concept of mole

Mole is nothing but the quantity of any substance which can be made of a huge number of atoms, molecules, ions, electrons, or any other forms of components in 12 grams of carbon. This quantity is specified as Avogadro’s number.

Molar mass

Molar mass is defined as the mass of one mole of any specific substance. Molar mass can convert particular grams of any specific substance to its moles. The molar mass has major applications in chemistry as well. It is very much simpler to calculate the number of moles in a substance if one knows its mass.

Avogadro’s hypothesis - Helpful for chemists

Amedeo Avogadro invented this hypothesis in 1811, in which he stated that the volume of gas can be seen independent of either mass or molecular size. Avogadro illustrates that irrespective of the chemical and physical properties, the equal volume of gas contained at the same temperature and pressure comprises an equal number of molecules. This law permitted the chemists to forecast the ideal gas performance.

Problems faced by Avogadro regarding his hypothesis

Scientists found that some of Avogadro’s principles were very difficult to understand because many of its concepts were quite difficult to grasp. Some famous chemists like Gay-Lussac, were not quite familiar with these kinds of behaviors of gases and found it difficult to understand and accept Avogadro’s theories.

To remedy this, Avogadro introduced the term called ‘molecules’ which can be referred to as the combinations of tiny particles. He also insisted on its origin, which is: the word molecule was derived from an old term ‘mole’ which means ‘lumps of matter’. Hence, a molecule can be viewed as a small cluster of matter.

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