20 points!! Find ∆H using Hess’s Law. Show your work.

PCI5(g) →PCI3(g) + Cl₂(g)

a. P4(s) + 6Cl₂(g) → 4PCl3(g); ∆H = -2439 kJ

b. P4(s) + 10Cl₂(g) → 4PCI5(g); ∆H = -3438 kJ