Question

calculate the number of molecules of oxygen present in 20 moles calcium carbonate

Answer 1

Given,
Number of moles of CaCO₃ = 20 moles
1 mole of CaCO₃ contains 3 moles of O
Therefore,
20 moles of CaCO₃ will contain 20 x 3 = 60 moles of O
1 mole of O contains 6.023 x 10²³ molecules
Hence,
60 moles of O = 60 x 6.023 x 10²³ atoms = 3.6138 x 10²⁵ atoms
As oxygen molecule (O₂) contains two oxygen atoms,
Number of oxygen molecules = (3.6138 x 10²⁵) / 2 = 1.8069 x 10²⁵ molecules