Consider the following equation:

Determine the bond enthalpy value for the F–S bond.

• A. -2301.0 kJ/mol
• B. 335.5 kJ/mol
• C. -1171.5 kJ/mol
• D. 1301.0 kJ/mol

Answer: (B)

Verified step by step guidance

1. Write the balanced chemical equation and note the given enthalpy change: \(\mathrm{H_2S (g) + 3 F_2 (g) \rightarrow SF_4 (g) + 2 HF (g)}\) with \(\Delta H = -1301 \ \mathrm{kJ/mol}\).
2. Identify all bonds broken and formed in the reaction. Bonds broken (reactants): 2 S–H bonds and 3 F–F bonds. Bonds formed (products): 4 F–S bonds and 2 F–H bonds.
3. Calculate the total bond energy of bonds broken using the given bond energies: \(2 \times 347 \ \mathrm{kJ/mol}\) for S–H and \(3 \times 159 \ \mathrm{kJ/mol}\) for F–F.
4. Calculate the total bond energy of bonds formed, except for the unknown F–S bond energy: \(2 \times 565 \ \mathrm{kJ/mol}\) for F–H bonds plus \(4 \times\) (unknown F–S bond energy).
5. Use the bond enthalpy relation: \(\Delta H = \text{Bonds broken} - \text{Bonds formed}\). Rearrange to solve for the unknown F–S bond energy: \(\text{F–S bond energy} = \frac{\text{Bonds broken} - \Delta H - \text{Energy of F–H bonds}}{4}\).