A student wants to have 3.011 × 1023 atoms each of magnesium and carbon elements. For this purpose, he will have to weigh:
6.022 × 1023 atoms of magnesium = one mole of magnesium
3.011 × 1023 atoms of magnesium = 0.5 moles of magnesium
Mass of magnesium = atomic weight x number of moles
Mass of magnesium = 24 × 0.5 = 12g
Similarly 6.022 × 1023 atoms of carbon = one mole of carbon
3.011 × 1023 atoms of carbon = 0.5 moles of carbon
Mass of carbon = atomic weight × number of moles
Mass of carbon = 12 × 0.5 = 6g