calculation - mole concept

Consider the Avogadro's number, NA = 6.02 X 1023

The number of mole of copper atoms

= (4.6 X 1023) / (6.02 X 1023)

= 0.764 mol

Molar ratio of copper to sulfur in copper (I) sulfur, Cu2S

= 2 : 1

Therefore, number of mole of sulfur

= 1/2 X 0.764

= 0.382 mol

Consider the molar mass of copper = 63.5 gmol-1

molar mass of sulfur = 32.1 gmol-1

Mass of copper (I) sulfur

= no. of mole of Cu X molar mass of Cu + no. of mole of S X molar mass of S

= (0.764)(63.5) + (0.382)(32.1)

= 60.8 g