Taking Avogadro’s number, N, to be 6.022×10²³, we can work out the mass of a C atom in grams.
C has an atomic weight of about 12 so the mass of the C atom is 12/N grams.
Similarly Ca (atomic weight 40) has a mass of 40/N grams and O (atomic weight 16) has a mass of 16/N grams.
The molecular weight of CaCO₃ is 40+12+48=100.
So the mass of a molecule of CaCO₃ is 100/N grams.
The mass of 4.52×10²⁴ atoms of C is 4.52×10²⁴×12/(6.022×10²³)=90.07g.
The mass of 4.52×10²⁴ molecules of CaCO₃ is 4.52×10²⁴×100/(6.022×10²³)=750.58g.