Energetics
28 past-paper questions on Energetics · examined 2020–2025.
20258 questions
© UCLES 2025 5070/11/O/N/25 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. N N + O 2 2H 2 O + N 2 H H H H A value for the enthalpy change, H , of this reaction is calculated by selecting and using data from the table. What is the value of H ? A –728 kJ / mol B –568 kJ / mol C –34 kJ / mol D +352 kJ / mol 7
Identify the energy changes labelled A and B in the reaction pathway diagram.
Use the reaction pathway diagram to explain why the decomposition of sodium hydrogencarbonate is endothermic.
Show by calculation that the enthalpy change of the reaction between methane and chlorine, ΔH, is –119 kJ / mol.
Complete the reaction pathway diagram for the reaction between methane and chlorine. Label the reactants, products, enthalpy change, and activation energy.
5070/22/M/J/25 © UCLES 2025 3 The equation for the reaction between ethene and bromine is shown in Fig. 3.1. H C H Br Br H C H Br C H H Br H C + H Fig. 3.1 (a) Describe the observation when ethene gas is bubbled through aqueous bromine. ................................................................................................................................................... ............................................................................................................................................. [1] (b) Table 3.1 shows some bond energies. Table 3.1 bond bond energy in
Identify the energy changes labelled A and B in the reaction pathway diagram.
Use the reaction pathway diagram to explain why the reaction is exothermic.
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