Question

. Calculate number of atoms is each of
the following. (Average atomic mass :
N= 14 u, S = 32 u)
a. 0.4 mole of nitrogen
b. 1.6 g of sulfur
​

Answer 1

Solution :-

a )

• Atomic mass = 14 g

• Avogadro's no = 6.023 x 10^23

• moles of N = 0.4

We know that ,

⟹ moles = no of atoms / Avogadro's no

On rearranging ,

⟹ no of atoms = moles x Avogadro's no

⟹ no of atoms = 0.4 x 6.023 x 10^23

⟹ no of atoms = 2.4 x 10 ^23 atoms

b )

• Atomic mass = 32 g

• Mass of Sulphur = 1.6 g

we know that ,

⟹ moles = mass / atomic mass

⟹ moles = 1.6 / 32

⟹ moles = 0.05

we know that ,

⟹ moles = no of atoms / Avogadro's no

On rearranging ,

⟹ no of atoms = moles x Avogadro's no

⟹ no of atoms = 0.05 x 6.023 x 10^23

⟹ no of atoms = 3.011 x 10 ^22 atoms