Final answer:
The enthalpy of the formation of hydrazine can be calculated by constructing a Hess's Law cycle using the given reaction enthalpies for hydrazine and ammonia.
Step-by-step explanation:
The enthalpy of the formation of hydrazine, N₂H₄(l), at 25°C and 1 atm pressure can be calculated using the given reaction:
3N₂H₄(l) → N₂(g) + 4NH₃(g)
The enthalpy change for this reaction is ΔH°ᵣₓₙ = -336 kJ/mol. It is important to note that the enthalpy of formation refers to the formation of 1 mole of the substance, so we need to divide the enthalpy change by the stoichiometric coefficient of N₂H₄ in the reaction, which is 3.
Therefore, the enthalpy of formation of hydrazine, N₂H₄(l), at 25°C and 1 atm pressure is:
ΔH°f = ΔH°ᵣₓₙ / 3 = -336 kJ/mol / 3 = -112 kJ/mol