Question

Question #2694b

Answer 1

The formula mass is 399.86 u.

Explanation:

The calculation might be easier if you first multiply all atoms inside the parentheses by the subscript 3.

Then `"Fe"_2("SO"_4)_3` becomes `"Fe"_2"S"_3"O"_12`.

Now, we can calculate the formula mass.

`bb("No."color(white)(m)"Atom"color(white)(mm)A_text(r)color(white)(mm) "Mass")`
`color(white)(l)2color(white)(mmml)"Fe"color(white)(mml)55.84color(white)(mll)111.68`
`color(white)(l)3color(white)(mmml)"S"color(white)(mmm) 32.06color(white)(mm)96.18`
`12color(white)(mmm)"O"color(white)(mmll)16.00color(white)(mll)192.00`
`color(white)(mmmmmmmll)"Total = 399.86"`

The formula mass is 399.86 u.