Question

chemical equation for formation of N2O5

Answer 1

If so, you could use Hess Law for this since the enthalpies of formation of the reactions is already given. They could be combined to end up with N2O5 

2( 2NO + O2 -> 2NO ) DeltaH1 
4NO2 + O2 -> 2N2O5 DeltaH2 
2( N2 + O2 -> 2NO ) DeltaH3 

Adding those formulas will result to the cancelation of NO and NO2. 

This will then result to the ff. formula: 

2N2 + 5O2 -> 2N2O5 

DeltaHformation = 2DeltaH1 + DeltaH2 + 2DeltaH3 

= 2(-114.1kJ) + (-110.2kJ) + 2(180.5kJ) 

DeltaHformation= 22.6 kJ