Liquid hydrazine, N2H4(l), is a rocket fuel. It combusts in oxygen gas to form nitrogen gas and liquid water: N2H4(l) + O2(g) -> N2(g) + 2H2O(l)

Use the following thermochemical equations to calculate the enthalpy change for the combustion of liquid hydrazine:

2NH3(g) + 3N2O(g) -> 4N2(g) + 3H2O(l) ΔH = -1010kJ

N2O(g) + 3H2(g) -> N2H4(l) + H2O(l) ΔH = -317kJ

2NH3(g) + 0.5O2(g) -> N2H4(l) + H2O(l) ΔH = -143kJ

H2(g) + 0.5O2(g) -> H2O(l) ΔH = -286kJ

Edit: For reference, the book says the answer is ΔH = -623kJ