For the reaction $2\text{NF}_3(g) \rightarrow 2\text{N}(g) + 6\text{F}(g)$ the standard enthalpy change is $\Delta H^{\circ} = +1668\ \text{kJ}$. What is the bond energy for the $\text{N}-\text{F}$ bond?
- A$-556\ \text{kJ mol}^{-1}$
- B$-278\ \text{kJ mol}^{-1}$
- C$+278\ \text{kJ mol}^{-1}$
- D$+556\ \text{kJ mol}^{-1}$