Question

calculate the no. of atoms in 0.8 g of iron. (Fe=56)

Answer 1

Given mass = 0.8g
Molecular mass = 56
No. of atoms = No. of moles *NA(Avagadro No.)*No. of atoms
Moles = Given mass / Molecular mass
= 0.8/56 =0.014
No. of atoms = 0.014*6.023*10^23*1
Which can be written as 0.014NA

Answer 2

Given,

molecular weight of Fe = 56 g

Weight of Fe given = 0.8g

To find,

No. of atoms in 0.8 g of iron

Solution,

No. of moles of Fe that weigh 56 g is 1.

Therefore, no. of moles of Fe that weigh 0.8 g is:

No. of moles = 0.8/56

No. of moles = 0.014 moles of Fe.

Now the no of atoms that exist in 1 mole of Fe is 6.022 x 10^23 atoms.

Therefore, the no. of atoms in 0.014 moles is

No. of atoms = 0.014 x 6.022 x 10^23

No. of atoms = 8.43 x 10^21 atoms

The number of atoms in 0.8 g of Fe is 8.43 x 10^21 atoms.