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Dissociation Enthalpies
Have a question that asks to calculate the dissociation enthalpy of the N-N bonds in N2O4 given that:
Formation of NO2 = 33.85kJ/mol
Formation of N2O4 = 9.67kJ/mol
2NO2 <-> N2O4
33.85 is the energy needed to form 2 x N-O bonds (can you use this? seeing as its technically not just O-N-O)
The overall enthalpy of the reaction is 9.67-(2*33.85) = -58.03
-58.03kJ/mol is required to break 2 x N=O into 2 x N-O and form 1 N-N
This is about as far as I got, any help and points in the right direction would be much appreciated
Formation of NO2 = 33.85kJ/mol
Formation of N2O4 = 9.67kJ/mol
2NO2 <-> N2O4
33.85 is the energy needed to form 2 x N-O bonds (can you use this? seeing as its technically not just O-N-O)
The overall enthalpy of the reaction is 9.67-(2*33.85) = -58.03
-58.03kJ/mol is required to break 2 x N=O into 2 x N-O and form 1 N-N
This is about as far as I got, any help and points in the right direction would be much appreciated
cptbigt
Have a question that asks to calculate the dissociation enthalpy of the N-N bonds in N2O4 given that:
Formation of NO2 = 33.85kJ/mol
Formation of N2O4 = 9.67kJ/mol
2NO2 <-> N2O4
33.85 is the energy needed to form 2 x N-O bonds (can you use this? seeing as its technically not just O-N-O)
The overall enthalpy of the reaction is 9.67-(2*33.85) = -58.03
-58.03kJ/mol is required to break 2 x N=O into 2 x N-O and form 1 N-N
This is about as far as I got, any help and points in the right direction would be much appreciated
Formation of NO2 = 33.85kJ/mol
Formation of N2O4 = 9.67kJ/mol
2NO2 <-> N2O4
33.85 is the energy needed to form 2 x N-O bonds (can you use this? seeing as its technically not just O-N-O)
The overall enthalpy of the reaction is 9.67-(2*33.85) = -58.03
-58.03kJ/mol is required to break 2 x N=O into 2 x N-O and form 1 N-N
This is about as far as I got, any help and points in the right direction would be much appreciated
I have no idea
Isn't it just O2N-NO2 ---> NO2 + NO2 = 2 x 33.85 - 9.67 = 58.03 kJ mol-1?
Bond breaking being endothermic...
Bond breaking being endothermic...
cptbigt
Lol I feel ilke a real idiot now, didn't occur to me to think of it like that 
No worries...I could be wrong, that seems a little too easy....
The next part of the question states:
Given that the bond dissocation enthalpies of O2, H2 and NH2 are 495.0, 436.0 and 941.8kJ/mol respectively, calculate bond energies for the N-O and N-H bonds in NO2 and NH2 respectively.
And that from the previous data: formation of NO2 = 33.85
formation of NH2 = 184.1
For N-O
2O2 + N2 -> 2NO2
Would it be:
H = energy of bonds broken - energy of bonds made
Energy of bonds made = energy of bonds broken - H
Energy of bonds made = (1931.8-(2*33))/4
= 466kJmol-1
Given that the bond dissocation enthalpies of O2, H2 and NH2 are 495.0, 436.0 and 941.8kJ/mol respectively, calculate bond energies for the N-O and N-H bonds in NO2 and NH2 respectively.
And that from the previous data: formation of NO2 = 33.85
formation of NH2 = 184.1
For N-O
2O2 + N2 -> 2NO2
Would it be:
H = energy of bonds broken - energy of bonds made
Energy of bonds made = energy of bonds broken - H
Energy of bonds made = (1931.8-(2*33))/4
= 466kJmol-1
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