Question

7. The molar heat of formation of NH.NO, (5) is - 367.54 kJ and those of N20 (8) and H20 (1) are + 81.46 kJ
and - 285.78 kJ respectively at 25°C and 1.0 atmospheric pressure. Calculate AH and AU for the reaction.
​

Answer 1

Answer:

ΔHo=ΔHf(products)o−ΔHf(reactants)

[ΔH(N2O)o+2×ΔH(H2O)o]−[ΔH(NH4NO3)o]

=81.46+2×(−285.78)−(−367.5)=−122.56kJ

We know that ΔH=ΔU+ΔnRT

ΔU=ΔH−ΔnRT

Δn=2,R=8.314×10−3kJmol−1K−1,T=298K

ΔU=−122.56−(1)(8.314×10−3)(298)=−125.037kJ