Question

Use the molar bond enthalpy data in the table to estimate the value of ΔH°rxn for the equation NH3 (g) +2O2 (g) > HNO3 (g) +H2O (g)

Answer 1

The given reactionisas follows: NH, (8)+20.(8)-HNO, (8)+Ho(g) (gH,O(g The structures of these moleclesareas follows:

The required molar bond enthalpy data is as follows: N-Hbond; 390kJ.mol-1 O-Obond: 502kJ.mol1 N-O bond: 201 kJ mol N=O bond: 607 kJ.mol- O-H bond: 464 kJ mol There are three N - H bonds in NH3. The energy required to break the 3 N - H bonds is In reactants, there are three N-H bonds in NH 3 and two O = O bonds in two moles of O 2 . Hence, дН f() astana) 3x390kJ mol 2x502 kJ mol 2174 kJ-mol-1 In products, there are 2N - Obonds,1N-Obond, 10-H bondin HNO3 and2O-H bondsin H O Hence, kJ mol1x 607 kJ mol+1 464 kJ-mol (products) 2x 201 + 2 × 464 kJ-mol-1 - 2401 kJ.mol1 AH°reaction-AH f(reactants) AH fiproducts) =2174 kJ-mor-2401kJ . mor -227kJ.mol-l Hence, AF1°reaction for the given reaction is - 227kJ mol-1