Question

According to the following reaction, how much energy is required to decompose 55.0 kg of Fe3O4? The molar mass of Fe3O4 is 231.55 g mol-1.
Fe3O4(s) → 3Fe(s) + 2O2(g) ΔrH° = +1118 kJ

Answer 1

The first step is to convert the 55 kg of Fe₃O₄ to moles by using the molar mass, that is, 231.55 g/mol (55 kg = 55000 gms),

55000 gms × 1 mole / 231.55 gms = 237.53 moles of Fe₃O₄

For the decomposition of every 1 mole of Fe₃O₄, +1118 kJ of energy is needed. Therefore, the energy needed to decompose 237.53 moles will be:

237.53 moles of Fe₃O₄ × 1118 kJ / 1 mole = 265558 kJ

Thus, there is a need of 265558 kJ of energy to decompose 55 kg of Fe₃O₄.