Answer: 268 grams
Step-by-step explanation:
Number of moles of SO3 = 3.35 moles
Molar mass of SO3 = (32 + (16 x 3)
= 32 + 48 = 80g/mole
(Molar mass was calculated using the mass number of Sulphur: 32, and oxygen: 16)
Now, recall that:
Number of moles = (mass/molar mass)
3.35 moles = Mass / 80g/mole
Mass = 3.35 moles x 80g/mole
Mass = 268 grams
Thus, the mass of 3.35 moles of SO3 is 268 grams