Question

Calculate the number of molecules of phosphorus [P4] present in 31 gram of phosphorus.

Answer 1

Molecular mass of P₄ = 124 g/mol.

i.e.

Mass of 1 mole ( 6.023 X 10²³) P₄ molecules = 124 g

Hence..

124 g P₄=6.023 x 10²³ P₄ molecules

so

1g P₄ =( 6.023 x 10²³)/(124) =0.25 x 10²³molecules

and

31 g P₄ = 0.25 x 10²³ x 31 = 1.5 x10²³ molecules.