Answer:
399.88
Explanation:
The molar mass is just the number of total mass of each atom of each element.
2 - Fe = (55.845 x 2) = 111.69
3 - S = (32.06 x 3) = 96.18
12 - O = (15.999 x 12) = 191.988
For oxygen, it's being added 12 times because there is 4 in the compound times the 3 on the outside.
Now, add all of them and you have your answer!
