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5.1 Exothermic and endothermic reactions

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Question 12

Hydrazine, N2H4\text{N}_2\text{H}_4N2​H4​, decomposes:

N2H4→N2+2H2\text{N}_2\text{H}_4 \rightarrow \text{N}_2 + 2\text{H}_2N2​H4​→N2​+2H2​

Each hydrazine molecule contains one N-N\text{N-N}N-N bond and four N-H\text{N-H}N-H bonds.

The table gives the bond energies.

BondBond energy in kJ/mol
N-N\text{N-N}N-N163
N-H\text{N-H}N-H391
N≡N\text{N}\equiv\text{N}N≡N945
H-H\text{H-H}H-H436
a.

Calculate the overall energy change for the decomposition of hydrazine.

[3]
b.

Explain what happens to the temperature of the surroundings as the hydrazine decomposes.

[2]
Markscheme

5.1 Exothermic and endothermic reactions Questions

  1. GCSE
  2. /Chemistry
  3. /5.1 Exothermic and endothermic reactions

85 exam-style questions on AQA GCSE Chemistry 5.1 Exothermic and endothermic reactions, covering 5.1.1 Energy transfer during exothermic and endothermic reactions, 5.1.2 Reaction profiles, and 5.1.3 The energy change of reactions. Each one has a worked solution and a mark scheme showing where the marks go.

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