<u>Answer:</u> The mass of sulfur trixoide is 0.0485 g
<u>Explanation:</u>
We are given:
Molecules of sulfur trixoide = 
According to mole concept:
number of molecules are present in 1 mole of a compound
So,
number of molecules will be present in = 
To calculate the number of moles, we use the equation:

Moles of sulfur trixoide = 
Molar mass of sulfur trioxide = 80 g/mol
Putting values in above equation, we get:

Hence, the mass of sulfur trixoide is 0.0485 g