What is the mass of 4.49 x 10º carbon dioxide, CO2, molecules?

To find this you have to find the molar mass of CO2 which you can get on the periodic table, 12 + 16 + 16 = 44 g/mol

4.49 x 10^0 / 44 g/mol = .1020 mol CO2

1 mol = 6.022 x 10^23 molecules (avogadros number)

so .1020 mol x 6.022 x 10^23 =
6.14 x 10 ^22 molecules CO2