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Born-Haber dilema

Hi everyone,

I have been given the following question (all numbers are kJ/mol ):

"Use the data below to calculate the electron affinity of chlorine":

Standard enthalpy of atomisation of potassium 90
First ionisation enthalpy of potassium 420
Bond dissociation enthalpy of chlorine 244
Lattice enthalpy of potassium chloride -706
Standard enthalpy of formation of potassium chloride -436

I've drawn out the Born-Haber cycle, and get a value of -484. However, the mark scheme says it's -362.

Please can someone explain this to me?

Reply 1

typicalvirgo

Double check the value for the bond dissociation. It's usually for Cl2, and we are only dealing with Cl here. So, 244 is wrong and it has to be 122. -484+122=-362 :tongue:

(edited 7 years ago)

Reply 2

Electrogeek

Original post by typicalvirgo

Double check the value for the bond dissociation. It's usually for Cl2, and we are only dealing with Cl here. So, 244 is wrong and it has to be 122. -484+122=-362 :tongue: