Consider the energy level diagram below

Here are the solutions to the questions:

2. (a) Consider the energy level diagram below
The overall reaction shown is the atomization of liquid phosphorus trichloride:

$$\text{PCl}_3\text{(l)} \to \text{P(g)} + 3\text{Cl(g)} \quad \Delta H = +982 \text{ kJ}$$

We can use Hess's Law by following the steps in the diagram:

1. Reverse of enthalpy of formation of $\text{PCl}_3\text{(l)}$: $$$$