Question

Calculate the value of the change of H ?

N2 + O2 -> N2O5

H2 + 1/2 O2 -> H2O Change of H = -285.8 kj/mol
N2O5 + H2O -> 2HNO3 Change of H = -76.6 kj/mol
1/2N2 + 3/2O2 + 1/2H2 -> HNO3 Change of H = -174.1kj/mol

Answer 1

........

Explanation:

First of all, the final reaction required is

`" "N_2 + 5/2O_2->N_2O_5" ..........(4)"`.

If we number the 3 reactions serially as `(1),(2),(3),` then `(4)` can be obtained as `2xx(3)-(1)-(2)`

Just plug in the values for the reactions, and you will get the value of `DeltaH` of reaction `(4)`.