Answer: The mass is 1030.692 grams (1.03 x 10^3 grams if you apply sig figs)
This is a units conversion problem, we'll first need the molar mass of ammonium sulfate: 132.14 g/mol
Then we can solve so that:
7.80 moles (132.14 g/moles) = 1030.692 grams
