Determining Lattice enthalpy only by Born Haber cycle ? Watch

saravananr
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Why is it impossible to determine lattice enthalpy directly by experiment when we are able to determine enthapy of formation experimentally ?

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GeorgeL3
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(Original post by saravananr)
Why is it impossible to determine lattice enthalpy directly by experiment when we are able to determine enthapy of formation experimentally ?

When you look at the definition of lattice enthalpy it becomes more clear why it is not possible to determine experimentally:
Lattice enthalpy is the change in energy when converting 1 mole of solid crystal to its scattered gaseous ions. (This is lattice dissociation, although lattice formation is also referred to generically as lattice enthalpy).

Producing gaseous ions which don't react with other things is extremely difficult and it would be nearly impossible to have to measure the enthalpy changes at the same time.

Instead it is much easier to calculate using the Hess cycle/Born-Haber cycle.

Also you must be careful, it is not always possible to determine enthalpy of formation experimentally either. The equations involved are often just theoretical such as the formation of benzene which won't actually occur as shown:

If you are still confused at all by it then take a look on Chemguide, you can find the answer to a great deal of chemistry questions on there.
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saravananr
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Thanks for ur wonderful answer . I have clearly understood it now ! Thanks
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