Hydrazine, a component of rocket fuel, undergoes combus- tion to yield N2 and H2O:
N2H41l2 + O21g2 S N21g2 + 2 H2O1l2 (b) Use the following information to set up a Hess’s law cycle, and then calculate ΔH° for the combustion reac- tion. You will need to use fractional coefficients for some equations.
2 NH31g2 + 3 N2O1g2 S 4 N21g2 + 3 H2O1l2
ΔH° = - 1011.2 kJ N2O1g2 + 3 H21g2 S N2H41l2 + H2O1l2
ΔH° = - 317.2 kJ 4 NH31g2 + O21g2 S 2 N2H41l2 + 2 H2O1l2
ΔH° = - 286.0 kJ
H2O1l2 ΔH°f = - 285.8 kJ>mol
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