What is the mass in grams of 3.25 mol fe2 (so4) 3?

The answer is 1296.75 g

Molar mass of Fe2 (SO4) 3 is the sum of atomic masses of its elements:

Mr (Fe2 (SO4) 3) = 2Ar (Fe) + 3Ar (S) + 12Ar (O)

Ar (Fe) = 55.84 g/mol

Ar (S) = 32.06 g/mol

Ar (O) = 16 g/mol

Mr (Fe2 (SO4) 3) = 2 * 55.84 + 3 * 32.06 + 12 * 16

= 111.68 + 96.18 + 192

= 399.9 g/mol

Thus there are 399.9 g in 1 mol and x grams in 3.25 mol:

399 g : 1 mol = x : 3.25 mol

x = 399 g * 3.25 mol : 1 mol

x = 1296.75 g