Chemistry · Oct / Nov 2025 · Paper 11 · Question 14

Some bond energy data are given in the table. | bond | bond energy / kJ/mol | |------|----------------------| | O–O | 150 | | O=O | 496 | | O–H | 460 | | N–H | 390 | | N–N | 160 | | N=N | 410 | | N≡N | 944 | | H–H | 436 | Hydrazine, N2H4, reacts with oxygen, as shown. [structure: H2N–NH2] + O2 → 2H2O + N2 A value for the enthalpy change, ΔH, of this reaction is calculated by selecting and using data from the table. What is the value of ΔH?

1. A–728 kJ / mol
2. B–568 kJ / mol
3. C–34 kJ / mol
4. D+352 kJ / mol

As printed in the paper