# [SOLVED] Can anyone help with lattice energy?

Can anyone help with lattice energy?

The overall energy involved in the formation of CsCl from Cs(s) and Cl2(g) is -443 kJ/mol. Given the following information:

* heat of sublimation for Cs is +76 kJ/mol,

* bond dissociation energy for 1/2 Cl2 is +121 kJ/mol,

* 1st ionization energy for Cs is +376 kJ/mol, and

* Electron affinity for Cl (g) is -349 kJ/mol.

what is the magnitude of the lattice energy for CsCl in kilojoules per mole?

Please, if you can explain it to me. Thanks!

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## The Best Answer for Can anyone help with lattice energy?

You're just playing, aren't you Danny?

I'm sure you know about Hess's Law and Born-Haber cycles...

Overall:

Cs(s) + ½Cl2(g) --> CsCl(s) .....ΔHf(CsCl(s)) = -443 kJ mol‾¹

Because enthalpy is a state function, it is invariant on the route by which that system state is reached. Hence, the overall reaction can be broken down into steps, each of which are experimentally favourable in the determination of their respective ΔH values. Thus:

Cs(s) + ½Cl2(g) --> Cs(g) + ½Cl2(g) .....ΔHsub(Cs) = +76 kJ mol‾¹

Cs(g) + ½Cl2(g) --> Cs(g) + Cl(g) .....BD(½Cl2) = +121 kJ mol‾¹

Cs(g) + Cl(g) --> Cs+(g) + e‾ + + Cl(g) .....IE1(Cs) = +376 kJ mol‾¹

Cs+(g) + e‾ + + Cl(g) --> Cs+(g) + Cl‾(g) .....EA(Cl) = -349 kJ mol‾¹

Cs+(g) + Cl‾(g --> CsCl(s) .....–Ulatt(CsCl) = unknown

So:

ΔHf(CsCl(s)) = ΔHsub(Cs) + BD(½Cl2) + IE1(Cs) + EA(Cl) – Ulatt(CsCl)

==> –Ulatt(CsCl) = ΔHf(CsCl(s)) - ΔHsub(Cs) - BD(½Cl2) - IE1(Cs) - EA(Cl)

= (-443) - (76) - (121) - (376) - (-349)

= -667kJ mol‾¹

The lattice energy of CsCl is calculated to be 667 kJ mol‾¹.

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## The Best Answer for Can anyone help with lattice energy?

Well, let's think about it. When you talk about lattice energy, you talk about the energy needed to essentially COMPLETELY break apart an ionic bond (ionic solid --> separate gaseous ions). So, really, the more energy you need to pull these ionic solids apart, the more stable they were originally (or, the lower in energy they originally were). Therefore, if a compound has a higher lattice energy, it is more stable. Hope this helps! =D

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The substance that has a higher lattice energy is the more stable substance as it will maintain the solid state longer. So X is the more stable substance as it will need a lot more energy to vaporize it.

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The above answer is wrong but the above steps are probably correct.

The magnitude of U = -667 Kj / mol.

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+1 vote