# Verify that the number of atoms Avagadro's constant

• MotoH
In summary: So the number of atoms/molecules in a mole of a substance is always the same, and equal to Avogadro's constant, 6.0225 x 10^23.In summary, Avogadro's constant is a very important physical constant used to describe the number of atoms or molecules in one mole of a substance. It is equal to 6.0225 x 10^23 and is defined as the amount of substance that contains the same number of elementary entities as there are atoms in 0.012 kilogram of carbon 12. This constant is used in various calculations and conversions in chemistry and physics.
MotoH
"verify that the number of atoms..." Avagadro's constant

## Homework Statement

One mole of a substance is defined as an amount, in grams, numerically equal to its molecular mass expressed in amu. (when we refer to a chemical element and not a compound, we use the atomic mass.) Verify that the number of molecules (or atoms) in one mole of any substance is the same, and is equal to 6.0225 x 10^23. This number, called Avogadro's constant, is a very important physical constant.

****************
I've just started trying to learn physics, and this problem appeared in one of the questions that are at the end of each chapter.
The book is "Alonso-Finn Fundamental University Physics. Book 1: Mechanics"
The question is question number 2.8
I am taking a physics course next year and would like to learn as much as I can before I go into the class.

## Homework Equations

Not sure what else is needed.

## The Attempt at a Solution

I've attempted a couple times but, I am not sure how to set up an equation properly as to get a result. The problem states that it will work with any substance, although I've been told that it only works for carbon-12? [6.0225x10^23 = 1 gram so 1 gram X 12amu = 12grams]

Any and all help to point me in the right direction is appreciated!

Thanks, John.

Hi, welcome to PF.
Sounds like a bit of a circular argument.
1 mole is defined as 6.02E23 of anything, and an AMU is defined so that 6.02e23 of them is a gram.

The carbon bit is mostly for convenience. Atoms come in different isotopes with different nuber of nuetrons and so different AMU masses. Carbon is handy because its mostly C12 and its (farily) easy to separate out other isotopes

mgb_phys said:
1 mole is defined as 6.02E23 of anything, and an AMU is defined so that 6.02e23 of them is a gram.

Not exactly - mole is so far defined as

The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.

(see http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf)

--

I've figured it out! Quite simple once I was pushed in the right direction.

Molar mass constant/ avogadro's constant or M(subscript)u/N(subscript)a

## Related to Verify that the number of atoms Avagadro's constant

Avogadro's constant, denoted by the symbol NA, is a physical constant that represents the number of particles (usually atoms or molecules) in one mole of a substance. It has a value of approximately 6.022 x 10^23 particles per mole.

## How was Avogadro's constant determined?

Avogadro's constant was first determined by Italian scientist Amedeo Avogadro in the early 19th century through his studies on the relationship between the volume of gases and the number of particles present. It was later refined by other scientists, such as Jean Perrin, through experiments involving electrolysis and X-ray crystallography.

## Why is Avogadro's constant important?

Avogadro's constant is important because it allows scientists to make accurate measurements and calculations involving the number of particles in a substance. It is also a fundamental constant in chemistry and is used in many equations, such as the ideal gas law and the mole concept.

## What is the relationship between Avogadro's constant and the number of atoms in a substance?

The relationship between Avogadro's constant and the number of atoms in a substance is that one mole of a substance contains Avogadro's constant number of atoms (or molecules). This means that the molar mass of a substance, expressed in grams, is equal to its atomic or molecular weight in atomic mass units.

## How is Avogadro's constant used in everyday life?

Avogadro's constant is used in everyday life in various ways, such as in the production of medicines, food and beverages, and consumer products. It is also used in industrial processes, such as in the production of plastics and other materials. Additionally, it is used in the fields of chemistry, physics, and biology for calculations and experiments.

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