Born Haber Cycle Question (Missing information?)

[IB`NOT`ez]

This question about the Born Haber Cycle is rather confusing, hoping someone can help.

ii) Use the data in the following table and from the data booklet to construct the Born-Haber cycle for sodium chloride, NaCl, and determine the lattice enthalpy of NaCl(s).

Na(s) + Cl2(g) → NaCl(g) ∆H = –411 kJ mol–1        <---- (I'm assuming this is the enthalpy change for formation)

Na(s) → Na(g) ∆H = +108 kJ mol–1         <------ (I'm assuming this is the atomization for Na value)

(Note: There is no other information from earlier in this question; this is all that's given)

So after using the data booklet, I got the ∆H(ionization energy) for Na, which is +496, then ∆H(electron affinity) for Cl, which is -349.

However, I can't complete my cycle as I'm lacking the bond dissociation of Chlorine value from 1/2Cl2(g) to Cl(g).

The mark scheme says something like this: 

lattice enthalpy  = –[(–411) – (+108) – (+494) – (+121) – (–364)]
= 770 (kJ mol–1)

I have the 411,108, 494, 364 (roughly from the new data booklet 349), but I don't have the +121 value. I thought about using the Bond enthalpy value for a Cl-Cl bond, however it's about 200~ so it doesn't come close, not to mention there's only one Chlorine atom the whole time.

How do I proceed?

Thanks, appreciate any help.

[Msj Chem]

The bond dissociation energy of Cl₂ is +242 kJmol^-1. Half of that is +121 kJmol^-1. 

By the way the enthalpy of formation equation should be: 

Na_(s) + 1/2Cl_2(g) ==> NaCl_(s)

 

Edited August 7, 2016 by Msj Chem

[IB`NOT`ez]

2 hours ago, Msj Chem said:

The bond dissociation energy of Cl₂ is +242 kJmol^-1. Half of that is +121 kJmol^-1. 

By the way the enthalpy of formation equation should be: 

Na_(s) + 1/2Cl_2(g) ==> NaCl_(s)

 

Ahhh, thanks! By the way, what is the proper IB name for that sage? I'm seeing a lot of different answers from Bind Dissociation Enthalpy of Chlorine to Bond Enthalpy of Chlorine to Half Dissociation of Chlorine. 

[Msj Chem]

I'd go with either bond dissociation energy or bond dissociation enthalpy. 

[IB`NOT`ez]

Just now, Msj Chem said:

I'd go with either bond dissociation energy or bond dissociation enthalpy. 

Oh alright. Thank you again for the help.