Is this question formulated correctly? If not, please fix it and return the output as a JSON of the form: {'question': 'question text'}. Here is the question: Calculate ΔH° for the reaction H2(g) + Br2(g) → 2 HBr(g) using bond energy values. The ΔH°f of HBr(g) is not equal to one-half of the value calculated. Account for the difference.

Verified step by step guidance

1. Step 1: Understand the problem. We need to calculate the enthalpy change (ΔH°) for the reaction using bond energies and then compare it to the standard enthalpy of formation (ΔH°f) of HBr(g).
2. Step 2: Write the balanced chemical equation: H2(g) + Br2(g) → 2 HBr(g).
3. Step 3: Identify the bonds broken and formed. Breaking bonds requires energy, while forming bonds releases energy. In this reaction, we break one H-H bond and one Br-Br bond, and form two H-Br bonds.
4. Step 4: Use bond energy values to calculate the total energy change. The formula is: ΔH° = Σ(Bond energies of bonds broken) - Σ(Bond energies of bonds formed).
5. Step 5: Compare the calculated ΔH° with the given ΔH°f of HBr(g). If they differ, consider factors such as experimental conditions or the precision of bond energy values that might account for the discrepancy.

Key Concepts

Bond Energy

Bond energy is the amount of energy required to break one mole of a bond in a gaseous substance. It is a crucial concept in thermochemistry, as it allows for the calculation of the enthalpy change (ΔH) of a reaction by summing the bond energies of the reactants and products. Understanding bond energies helps explain why the calculated ΔH° may differ from standard formation enthalpies.

Enthalpy of Formation (ΔH°f)

The enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a specific type of enthalpy change that provides a reference point for calculating the energy changes in chemical reactions. The discrepancy mentioned in the question arises because ΔH°f values account for the stability of the compound in its standard state, which may not directly correlate with bond energies.

Thermochemical Equations

Thermochemical equations represent the relationship between heat and chemical reactions, indicating the enthalpy change associated with a reaction. These equations are essential for understanding how energy is absorbed or released during a reaction. The question highlights the importance of accurately interpreting these equations to reconcile differences between calculated bond energies and experimentally determined ΔH°f values.