The answer in Study Question 95 does not exactly match the value for the bond dissociation enthalpy of P—Cl in Table 8.8. The reason is that the numbers in the table are averages, derived from data on a number of different compounds. Values calculated from different compounds do vary, sometimes widely. To illustrate this, let’s do another calculation. Next look at the following reaction:The enthalpy of formation of PCl₅(g) is −374.9 kJ/ mol. Use this and Δ_f H° of PCl₃(g) to determine the enthalpy change for this reaction. Then, use that value of Δ_rH°, along with the bond dissociation enthalpy of Cl₂, to calculate the enthalpy change for the formation of a P—Cl bond in this reaction.

Data given in Question 95

White phosphorus exists as P₄ molecules with phosphorus atoms at the corners of a tetrahedron.

Data given in Table 8.8

Transcribed Image Text:

PC13(g) + Cl₂(g) → PC15(g)