Question

Calculate the number of molecules of sulphur (S₈) present in 64 g of solid sulphur. (Given: At. Mass of S=32 u)

Answer 1

Given: At. Mass of S = 32 u

Atomic mass of S₈ = 8 × 32u = 256u

1 mole of Al atom = 6.022 × 10²³ atoms

This means 265g of S8 has 6.022 × 10²³ molecules

Then 64g g contains:

Number of S₈ molecules = \(\frac{Given\,mass}{Molar\,mass}\)x 6.022 x 10²³

Number of S₈ molecules = \(\frac{64g}{256u}\)x 6.022 x 10²³

⇒ Number of S₈ molecules = 1.5 x 10²³ molecules

Thus, the number of molecules of sulphur (S₈) is 1.5 x 10²³ molecules.