How was avagadros number was calculated

  • Thread starter SSJ2
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In summary, the calculation of Avogadro's number is based on the mass of 12 grams of carbon-12 and the fact that there are 6.02*10^23 atoms in this amount. This number was determined experimentally and cannot be calculated. Additionally, the law stating that equal volumes of different gases at the same temperature and pressure contain the same number of particles is only valid on average and can have deviations when considering a small number of atoms. The volume of a gas is determined by the distance between atoms, which can be safely ignored if the density is low enough.
  • #1
SSJ2
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i guess i have two questions...

1) the first is although I know the calculation of the number is based around the mass of 12 grams of carbon-12 and that there are 6.02*10^23 atoms here. How was it found that this many atoms of carbon was found in the 12 grams?



2) my second question is more based on his law which states "equal volumes of different gases at the same temperature and pressure contain the same number of particles."
referenced here
http://www.scientificamerican.com/article.cfm?id=how-was-avogadros-number

now my question here is that let's say we have a very small finite volume that can hold 10 hydrogen atoms, and assuming that the temperatures are equal and pressure is equal

how can the same volume hold the same number of atoms of radon which is much larger than hydrogen?
 
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  • #2
SSJ2 said:
i guess i have two questions...

1) the first is although I know the calculation of the number is based around the mass of 12 grams of carbon-12 and that there are 6.02*10^23 atoms here. How was it found that this many atoms of carbon was found in the 12 grams?



2) my second question is more based on his law which states "equal volumes of different gases at the same temperature and pressure contain the same number of particles."
referenced here
http://www.scientificamerican.com/article.cfm?id=how-was-avogadros-number

now my question here is that let's say we have a very small finite volume that can hold 10 hydrogen atoms, and assuming that the temperatures are equal and pressure is equal

how can the same volume hold the same number of atoms of radon which is much larger than hydrogen?

I'll answer number 2 for you: that law is only valid as a statistical statement. That is to say that the law only holds on average. However, if you have a very large number of gas particles, the pressure and volume are always very very close to their average values, so you don't notice any deviations from the law. However, if you consider such a small number of atoms, statistical fluctuations will be large and you can much more easily see deviations from the "law".
 
  • #3
In the gas, as long as the density is low enough, distance between atoms is so large their volume can be safely ignored.

Avogadro's constant is not something that can be calculated - it is something that has to be determined experimentally. Consult prof. Google.
 

1. How was Avogadro's number calculated?

Avogadro's number was calculated by French scientist Amedeo Avogadro in the early 19th century. He proposed that the volume of a gas at a given pressure and temperature is directly proportional to the number of molecules present. This led to the idea that at a certain pressure and temperature, equal volumes of different gases would contain the same number of molecules. Avogadro used this principle to calculate the number of molecules in one mole of a gas, which is now known as Avogadro's number.

2. What is the value of Avogadro's number?

The value of Avogadro's number is approximately 6.022 x 10^23. This means that one mole of any substance contains 6.022 x 10^23 particles, whether they are atoms, molecules, or ions.

3. How is Avogadro's number used in chemistry?

Avogadro's number is a fundamental constant in chemistry and is used to convert between the microscopic scale of atoms and molecules, and the macroscopic scale of grams and moles. It is also used to determine the molar mass of a substance, which is the mass of one mole of that substance.

4. Can Avogadro's number be experimentally determined?

Yes, Avogadro's number can be experimentally determined by measuring the number of particles in a known volume of gas at a specific pressure and temperature. This method is known as the "Avogadro experiment" and has been performed numerous times, with the most recent determination giving a value of 6.02214076(12) x 10^23.

5. Why is Avogadro's number important in the study of matter?

Avogadro's number is important in the study of matter because it allows scientists to relate the number of particles in a substance to its mass. This helps in understanding the properties and behavior of matter at the atomic and molecular level, and is crucial in fields such as chemistry, physics, and materials science.

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