Hydrazine (N2H4\text{N}_2\text{H}_4N2H4) is used as a rocket propellant. It undergoes combustion according to the following equation:
N2H4(g)+O2(g)→N2(g)+2H2O(g) \text{N}_2\text{H}_4(\text{g}) + \text{O}_2(\text{g}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\text{g}) N2H4(g)+O2(g)→N2(g)+2H2O(g)Mean bond enthalpies are given in the table below:
| Bond | Mean bond enthalpy / kJ mol−1\text{kJ mol}^{-1}kJ mol−1 |
|---|---|
| N−N\text{N}-\text{N}N−N | +163 |
| N−H\text{N}-\text{H}N−H | +391 |
| O=O\text{O}=\text{O}O=O | +496 |
| N≡N\text{N}\equiv\text{N}N≡N | +945 |
| O−H\text{O}-\text{H}O−H | +463 |
What is the enthalpy change, in kJ mol−1\text{kJ mol}^{-1}kJ mol−1, for this combustion reaction?
−737 kJ mol−1-737\text{ kJ mol}^{-1}−737 kJ mol−1
−574 kJ mol−1-574\text{ kJ mol}^{-1}−574 kJ mol−1
+574 kJ mol−1+574\text{ kJ mol}^{-1}+574 kJ mol−1
+352 kJ mol−1+352\text{ kJ mol}^{-1}+352 kJ mol−1
