Chapter 6, Problem 6.77QP

Hydrazine, N₂H₄, is a colorless liquid used as a rocket fuel. What is the enthalpy change for the process in which hydrazine is formed from its elements?

${\text{N}}_2(g)+2{\text{H}}_2(g)\to {\text{N}}_2{\text{H}}_4(l)$

Use the following reactions and enthalpy changes:

$\begin{array}{l}{\text{N}}_2{\text{H}}_4(l)+{\text{O}}_2(g)\to {\text{N}}_2(g)+2{\text{H}}_2\text{O}(l);\hfill \\ \Delta H=-622.2\text{kJ}\hfill \\ {\text{H}}_2(g)+\frac{1}{2}{\text{O}}_2(g)\to {\text{H}}_2\text{O}(l);\Delta H=-285.8\text{kJ}\hfill \end{array}$