Question

What would you multiply "grams of iodine" by to get the units "atoms of iodine" ?

What would you multiply "grams of sulfur" by to get the units "atoms of sulfur" ?

What would you multiply "atoms of rubidium" by to get the units "grams of rubidium" ?

Answer 1

First see , the concept of moles and Avogadros number through that, you can calculate number of atoms in any element.

To calculate number of atoms in sample , you need to calculate number of moles of element in the sample. We know that, 1mole of any sample ,contains 6.023 x 10 ²³ atoms, so must know the mass and molar mass of that particular element. Figure 6.023 x 10²³  is called as Avogadros number .

Now let's see answer to particular question -

1)number of atoms of iodine = ?

For example , mass of iodine samples =1.0 g

Atomic mass of iodine =

Now we have to calculate number of moles of iodine (n) =

=Mass (m) /atomic  mass of iodine (M)

= 1.0 g /126.90 g/mol

= 0.007880 mol

Now we can use Avogadros number for determination of number of atoms -

Number of iodine atoms = number of moles (n) x Avogadros number

= 0.007880 mol x 6.023 x 10 ²³

=4.74 x 10 ²¹ atoms of iodine

2)number of atoms in sulphur = ?

Mass of sulfur sample = 1.0 g

Atomic mass of sulfur = 32.065 g/mol

Number of atoms = (1.0 g/32.065 g/mol) x 6.023 x 10²³

=1.88 x 10 ²² atoms of sulfur

3)number of atoms of rubidium =?

Mass of rubidium sample = 1.0 g

Atomic mass of rubidium = 85.46 g/mol

So number of atom of rubidium(n)=

= (1.0g /85.46 g/mol)x 6.023 x 10²³

= 7.05 x 10²¹ atoms of rubidium