# Calculate the number of atoms in each of the following? (a) 52 moles of Ar (b) 52u of He (c) 52g of He

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Updated on: September 25th, 2023

The number of atoms in 52 moles of Ar is 3.13144 x 1025 atoms of Ar, 52u of He is 13 atoms, and 52g of He is 7.829 x 1024 atoms. In order to calculate the number of atoms in a formula, one must take into account the sample’s weight, its atomic mass from the periodic table, and a variable known as Avogadro’s number.

### Number of atoms in 52 moles of Ar

1 mole of Ar = 6.022 x 1023 atoms of Ar

52 moles of Ar = 52 x 6.022 x 1023

52 moles of Ar = 3.13144 x 1025 atoms of Ar

### Number of atoms in 52u of He

The atomic mass of He = 4 amu

52u of He = 52/4 = 13 atoms

### Number of atoms in 52g of He

1 mole of He = 4g

= 6.022 x 1023 atoms of He

52g of He = 52/4 = 13 moles

Number of atoms in 13 moles of He = 13 x 6.022 x 1023 atoms

Number of atoms in 13 moles of He = 78.29 x 1023 atoms

52g of He = 7.829 x 1024 atoms

### Significance of Avogadro’s number

• A substance’s mass is measured at the atomic level using an atomic mass unit. The definition of an atomic mass unit is the weight of one carbon atom divided by twelve.
• For instance, hydrogen has an atomic mass unit of 1.00794 amu. It is not feasible to determine an atom’s, electron’s, or molecule’s capacity to, say, carry out a reaction.

Summary:

## Calculate the number of atoms in each of the following? (a) 52 moles of Ar (b) 52u of He (c) 52g of He

The number of atoms in 52u of He is 13 atoms, 52 moles of Ar is 3.13144 x 1025 atoms of Ar, and 52g of He is 7.829 x 1024 atoms. One must consider the sample’s weight, its atomic mass from the periodic table, and a factor known as Avogadro’s number in order to determine the number of atoms in a formula.

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