1. Find the molar mass of each of the molecules
CO2 = 12g + 2(16g) = 44g
H2O = 2(1g) + 16g = 18g
2. Apply the formula: Mass = No. of moles x Molar Mass
Mass of CO2 = 5 x 44g = 220g
Mass of H2O = 5 x 18g = 90g
220g>90g and thus the mass of five moles of CO2 > the mass of five moles of H2O.