What is #Delta"E"# for the formation of gaseous sodium and chloride ions from gaseous sodium and chlorine atoms?

1 Answer
Meave60
Feb 20, 2015

The #Delta"E"# is #"147.0 kJ/mol"#.

#Delta"E"# for the formation of gaseous sodium and chloride ions from gaseous sodium and chlorine atoms is the sum of the first ionization energy (I.E.) for gaseous Na, and the electron affinity (E.A.) of a chlorine atom in the gaseous state for an electron.

#Delta"E" = "I.E"#. + #"E.A."#

The following data comes from http://chemed.chem.purdue.edu/demos/demosheets/7.1.html.

1st Ionization Energy [#"Na"("g")# #rarr# #"Na"^+("g")# + #"e"^-#]: #"495.8 kJ/mol"#

Electron Affinity [#"Cl(g)"# + #"e"^-# #rarr# #"Cl"^-""("g")#]: #-348.8# #"kJ/mol"#

#Delta"E"# = #"495.8 kJ/mol"# + #(-348.8)##"kJ/mol"# = #"147.0 kJ/mol"#

Note: I included only the data that started with the sodium and chlorine atoms in the gaseous state, and ended with the formation of the gaseous sodium and chloride ions.

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