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

Thread starter cuallito
Start date Nov 15, 2021
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Energy Lattice

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The lattice energy calculation for PbCl2 using Hess's Law resulted in -1770 kJ, while the expected value is -2484 kJ. The discrepancy arose from not flipping the sign for the reaction 2Cl(g) -> Cl2(g). Despite correcting this, the calculated value still did not match the book's answer. There is speculation that the book may contain an error. Accurate calculations are crucial for understanding lattice energy in ionic compounds.

Nov 15, 2021

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.

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Nov 15, 2021

cuallito

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

Nov 16, 2021

mjc123

Science Advisor

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

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