The number of atoms or molecules in one mole of a substance is defined as Avagadro's number
The Avagadro's number is 6.023 X 10^23 atoms / molecules
Given:
The moles of carbon dioxide = 0.15 moles
In order to calculate the number of molecules in given moles of carbon dioxide we will multiply the given moles with Avagadro's number as
Number of molecules = 0.15 X 6.023 X 10^23
Number of molecules = 9.035 X 10^22 molecules of carbon dioxide