Final answer:
To determine the energy evolved for 816 g of Al2O3, calculate the number of moles of Al2O3 formed and then use the enthalpy change of −851.5 kJ/mol to find the total energy. The correct answer is 6.82×103 kJ. option c is correct.
Step-by-step explanation:
The student has asked how much energy is evolved during the formation of 816 g of Al2O3 according to the given reaction. The reaction has an enthalpy change (ΔH) of −851.5 kJ when 1 mole of Fe2O3 and 2 moles of Al react to form 2 moles of Fe and 1 mole of Al2O3. To find out the energy evolved for 816 g of Al2O3, we first need to calculate the number of moles of Al2O3 formed.
The molar mass of Al2O3 (Aluminum oxide) is 101.96 g/mol (26.98 g/mol for Al and 16.00 g/mol for O). We can find the moles of Al2O3 by dividing the given mass by the molar mass:
Moles of Al
2
O
3
= 816 g ÷ 101.96 g/mol
Next, we use the ratio of the energy change for the formation of 1 mole of Al2O3 (which is −851.5 kJ for the reaction of the moles of reactants specified in the balanced chemical equation) to calculate the total energy change.
After making these calculations, we find that the energy evolved for the formation of 816 g of Al2O3 is 6.82×103 kJ, which corresponds to option c.