Determination of lattice energy of an ionic compound

[mcfaker]

Hi,

In my book it says that it is difficult to determine the lattice energy of NaCl so they use the Haber cycle which applies Hess' law.
Lattice is the energy change when a solid ionic substance separates into ions in gas phase.

We could simply increase tempetrature until NaCl breaks down into ions & then calculate the heat that has been absorbed. So why do they say that it is difficult to determine the lattice?
Is it because we must achieve very high temperatures to melt salt?


Thank you for helping me.

 

[Sunil Simha]

The direct measurement of lattice energy is not possible as prescribed by your method because it is difficult to keep the oppositely charged gaseous ions from clumping together for a stretch of time. As they clump, they release energy and now even more energy has to be supplied to break it and thus the final value wouldn't be accurate.

 

[mcfaker]

Thank you my man :)