Question

An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g) Calculate DH°rxn for this reaction. DH°f [NH3(g)] = –45.9 kJ/mol; DH°f [NO(g)] = 90.3 kJ/mol; DH°f [H2O(g)] = –241.8 kJ/mol

Answer 1

Answer:

The ΔH°rxn for this reaction is -905.9 kJ

Explanation:

Step 1: Balanced reaction:

4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g)

Step 2: Given data

ΔH°f [NH3(g)] = –45.9 kJ/mol

ΔH°f [NO(g)] = 90.3 kJ/mol

ΔH°f [H2O(g)] = –241.8 kJ/mol

ΔH°f of O2 is defined to be zero

Step 3: Calculate ΔH°rxn

ΔH°rxn = ΔH°products - ΔH°reactants

ΔH°rxn = ((4*90.3) + 6*-(241.8)) - 4*(-45.9) = -905.9 kJ

The ΔH°rxn for this reaction is -905.9 kJ