Posted by jessica on .
4.72 moles of sulfur trioxide molecules contain how many oxygen atoms?
i know the answer is 8.53 x 10^24
but i do know how my professor got it
**this is one of my practice exam question!

chemistry 
DrBob222,
1 mol of a molecule contains 6.022E23 molecules. You have 4.72 moles; therefore,
4.62 x 6.022E23 = 2.842E24 molecules of SO3. There are 3 atoms of oxygen per 1 molecule of SO3; therefore, the number of oxygen atoms must be 3 times that or
2.842E24 x 3 = 8.527E24 which rounds to 8.53E24 to 3 significant figures.