Answer:1.12 g
Explanation:Molar mass of compound ​FeSO4(NH4)2SO4.6H2O = 392.14 g mol-1
Number of moles of compound in 7.84g sample = 7.84 g/ 392.14 g mol-1
= 0.02 mole
1 mole of sample contain 1 mole of Fe
So, 0.02 mole of sample would contain 0.02 moles of Fe.
Mass of Fe equivalent to 0.02 mole = 0.02 mol x molar mass of Fe
= 0.02 mol x 55.84 g mol-1
= 1.12 g