Question

Consider the reaction: 2Al(s) + Fe_{2}O_{3}(s) → 2Fe(s) + Al_{2}O_{3}(s), ΔH_{rxn} = -851.5 kJ/mol. If 75 g of aluminum are reacted with excess iron(III) oxide, how much heat (in kilojoules) is produced?

Answer 1

If 75 g of aluminum are reacted with excess iron(III) oxide, the amount of heat produced is -1184.4 kJ.

Step-by-step explanation:

The given reaction is: 2Al(s) + Fe₂O₃(s) → 2Fe(s) + Al₂O₃(s). The enthalpy change for this reaction is -851.5 kJ/mol of Fe₂O₃. We can use this value to calculate the amount of heat produced when reacting a specific amount of aluminum.

If 75 g of aluminum are reacted with excess iron(III) oxide, we need to first convert the mass of aluminum to moles using its molar mass. The molar mass of aluminum is 26.98 g/mol. Thus, 75 g of aluminum is equal to 75 g * (1 mol/26.98 g) = 2.78 mol of Al. Since 2 mol of Al are consumed in the balanced chemical equation, the moles of Al reacted will produce half the amount of heat, resulting in a heat production of -851.5 kJ/mol * 2.78 mol / 2 = -1184.4 kJ.