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

Quizplus · Accepted Answer

According to Hess's law, the enthalpy change for a reaction is equal to the sum of the enthalpy changes of the reactions that make up the overall reaction. Therefore, we can use the enthalpies of formation of the reactants and products to calculate the enthalpy change for the overall reaction.

The enthalpies of formation for Al (s), O2 (g), and S (s) are zero by definition. The enthalpy of formation for SO3 (g) is -395 kJ/mol. Using these values, we can calculate the enthalpy of formation for Al2(SO4)3 (s) as follows:

2Al (s) + 3O2 (g) + 3/2S (s) → Al2(SO4)3 (s)
ΔH°f = 2(0 kJ/mol) + 3(-395 kJ/mol) + 3/2(0 kJ/mol) - (-3351 kJ/mol)
ΔH°f = -1676 kJ/mol

Therefore, the answer is B) -1676.

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