The value of ΔH° for the following reaction is -3351 kJ: 2Al (s) + 3O₂(g) → 2Al₂O₃(s)
The value of ΔH°_f for Al₂
(s) is ________ kJ.

Question

The value of ΔH° for the following reaction is -3351 kJ: 2Al (s)+ 3O₂(g)→ 2Al₂O₃(s) The value of ΔH°_f for Al₂ (s)is ________ kJ. A)-3351 B)-1676 C)-32.86 D)-16.43 E)+3351

Quizplus · Accepted Answer

According to the given reaction, 2 moles of Al and 3 moles of O2 react to form 2 moles of Al2O3 with the release of -3351 kJ of heat. 
This means that when 1 mole of Al2O3 is formed, -3351/2 = -1675.5 kJ of heat is released.
Therefore, the ΔH°f for Al2O3 is -1675.5 kJ/mol.
So, the answer is B) -1676 kJ/mol (rounded off to two decimal places).

The Value of ΔH° for the Following Reaction Is -3351