how much does 4.97×10^21 molecules of CO2 weigh?

Avogadro constant = 6.022 × 10²³ /mol
Moles of CO₂ = (4.97 × 10²¹ molecules) / (6.022 × 10²³ molecules/mol) = 0.00825 mol

Molar weight of CO₂ = (12.0 + 16.0×2) g/mol = 44.0 g/mol
Weight of CO₂ = (0.00825 mol) × (44.0 g/mol) = 0.363 g

OR:
(4.97 × 10²¹ CO₂ molecules) × (1 mol / 6.022 × 10²³ molecules) × (44 g / 1 mol)
= 0.363 g CO₂