Hydrazine, N₂H₄, May Be Produced by the Reaction
2 NH₃(g) $\rightarrow$

Hydrazine, N₂H₄, may be produced by the reaction
2 NH₃(g) + H₂O₂(l) $\rightarrow$ N₂H₄(l) +H₂O(l)
Use the following data for the standard enthalpies of formation at 298 K for the various species to calculate the standard enthalpy of reaction at this temperature.
$\Delta$ _fH^o / (kJ mol^-1
NH₃(g) -46
H₂O₂(l) -188
N₂H₄(l) +51
H₂O(l) -286

A) +45 kJ mol^-1
B) -139 kJ mol^-1
C) -1 kJ mol^-1
D) -469 kJ mol^-1