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Enthalpy changes

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Question 23

The reaction of nitrogen gas with fluorine gas to produce nitrogen trifluoride gas is represented by the equation below:

N2(g)+3F2(g)→2NF3(g)ΔrH=−228 kJ mol−1 \text{N}_2(\text{g}) + 3\text{F}_2(\text{g}) \rightarrow 2\text{NF}_3(\text{g}) \quad \Delta_r H = -228 \text{ kJ mol}^{-1} N2​(g)+3F2​(g)→2NF3​(g)Δr​H=−228 kJ mol−1

Using the bond enthalpy data provided, what is the average bond enthalpy of the N−F\text{N}-\text{F}N−F bond in NF3\text{NF}_3NF3​?

  • Bond enthalpy of N≡N=+945 kJ mol−1\text{N}\equiv\text{N} = +945 \text{ kJ mol}^{-1}N≡N=+945 kJ mol−1
  • Bond enthalpy of F−F=+158 kJ mol−1\text{F}-\text{F} = +158 \text{ kJ mol}^{-1}F−F=+158 kJ mol−1
A

+274.5 kJ mol−1+274.5 \text{ kJ mol}^{-1}+274.5 kJ mol−1

B

+198.5 kJ mol−1+198.5 \text{ kJ mol}^{-1}+198.5 kJ mol−1

C

+549.0 kJ mol−1+549.0 \text{ kJ mol}^{-1}+549.0 kJ mol−1

D

−274.5 kJ mol−1-274.5 \text{ kJ mol}^{-1}−274.5 kJ mol−1

Markscheme

Enthalpy changes Questions

  1. A Level
  2. /Chemistry
  3. /Enthalpy changes

31 exam-style questions on OCR A A Level Chemistry Enthalpy changes. Each one has a worked solution and a mark scheme showing where the marks go.

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