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.
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.