Why is My Lattice Energy Calculation for PbCl2 Different from the Book's?

[cuallito]

Homework Statement

Determine the lattice energy of PbCl2

Relevant Equations

Lattice energy= Heat of formation- Heat of atomization- Dissociation energy- (sum of Ionization energies)- (sum of Electron Affinities)

Here's my attempt at solving it using Hess's Law. I get -1770kJ when I add up all the numbers. The correct answer is supposed to be -2484 kJ.

 

[cuallito]

I forgot to flip the sign for 2Cl(g)->Cl2(g), but I'm still not getting the right number:

 

[mjc123]

I agree with your calculation. Maybe the book's wrong - it happens.