Question

Use Hess's Law or the summation equation to calculate the ΔHrxn. Round to the nearest tenth!!

Answer 1

The ΔHrxn with the nearest tenth will have value of -60 K.

Explanation:

NF(g) + ___F2 (g) --> ___NF2 (g

data given:

½N2 (g) + ½F2 (g) -> NF (g) Hf = 86.6 kJ

½N2 (g) + F2 (g) -> NF2 (g) Hf = 33.8 kJ

Hess's law of heat is summation says that total change in enthalpy during a reaction is same whether the reaction is direct or in various steps.

½N2 (g) + ½F2 (g) -> NF (g) Hf = 86.6 kJ

reversing the equation we get:

NF  -> ½N2 (g) + ½F2 (g)

Heat of enthalpy becomes negative so -86.6 KJ

Now adding both the reactions:

NF  -> ½N2 (g) + ½F2 (g)

½N2 (g) + F2 (g) -> NF2 (g) Hf = 33.8 kJ

Removing the common entities from the reaction we get

F2 (g) + NF (g) --> ½F2 (g) +  NF2 (g) Hf

the summation of enthalpy is

-86.6+ 33.8

= 52.8 KJ

The nearest tenth will be -60 KJ.