1021 molecules are removed from 200 mg of CO2. The moles of CO2 left is

1021 molecules =1021 molecule 6.022×1023 molecule /mol=1.66x10−3 mol 200 mg of CO2=200×10−3g44g/mol=4.54×10−3mol.The number of moles of CO2 remaining = (4.54 -1.66) x 10-3 = 2.88 x 10-3.