Determine the number of chromium atoms in 46.2 gram of chromium oxide

Question

Formula is Cr2O3

Answer 1

Cr = 51.996 g/mole x 2 = 103.932 g

O = 15.999 g/mole x 3 = 47.997 

Total = 151.929 g/mole Cr₂O₃

46.2 g x 1 mole/151.929 g x 6.02x10²³ formula units/mole = 1.83x10²³ formula units

Each formula unit contains 2 atoms of Cr  

Total number of Cr atoms = 2 x 1.83x10²³ = 3.66x10²³ atoms