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IB Chemistry HL 2.2.7 Energy profiles Question Bank

Practise IB Chemistry HL 2.2.7 by applying energy profiles to exam-style questions.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • identify the relevant chemical structure, process or evidence
  • apply the correct chemical model or equation
  • evaluate the result using chemical reasoning and data

2.2.7 (HL)—Energy profiles question 1

[Maximum number: 2]

The reaction between hydrogen and nitrogen monoxide is thought to proceed by the mechanism shown below.

2NO( g)⇌N2O2( g) fast equilibrium N2O2( g)+H2( g)→N2O( g)+H2O( g) slow reaction N2O( g)+H2( g)→N2( g)+H2O( g) fast reaction \begin{array}{ll} 2 \mathrm{NO}(\mathrm{~g}) \rightleftharpoons \mathrm{N}_{2} \mathrm{O}_{2}(\mathrm{~g}) & \text { fast equilibrium } \\ \mathrm{N}_{2} \mathrm{O}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \rightarrow \mathrm{N}_{2} \mathrm{O}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g}) & \text { slow reaction } \\ \mathrm{N}_{2} \mathrm{O}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \rightarrow \mathrm{N}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g}) & \text { fast reaction } \end{array}

The enthalpy change for the reaction between nitrogen monoxide and hydrogen is -664 kJ and its activation energy is 63 kJ .

Sketch the potential energy profile for the overall reaction, using the axes given, indicating both the enthalpy of reaction and activation energy.

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