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IB Chemistry HL 1.2.5 Born-Haber cycle Question Bank

Practise IB Chemistry HL 1.2.5 by applying born-haber cycle 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

1.2.5 (HL)—Born-Haber cycle question 1

[Maximum number: 3]

Magnesium, a reactive metal found in many common minerals, is also an essential nutrient for both plants and animals.

Question (a)

(a)

Although magnesium is usually found as Mg2+\mathrm{Mg}^{2+} in its compounds, it is possible to use the Born-Haber cycle to investigate the possibility of Mg+\mathrm{Mg}^{+}being able to form stable compounds.

Use the ionization energy data from part (b), along with the other data provided below, to determine the enthalpy change of formation of MgCl(s). Assume that, because Mg+\mathrm{Mg}^{+} would be similar in size to Na+,MgCl\mathrm{Na}^{+}, \mathrm{MgCl} would have a similar lattice enthalpy to NaCl .

 Enthalpy of atomization of Mg +146 kJ mol−1 Bond enthalpy in Cl2+243 kJ mol−1 Electron affinity of Cl−349 kJ mol−1 Lattice enthalpy of NaCl+790 kJ mol−1\begin{array}{ll} \text { Enthalpy of atomization of Mg } & +146 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \text { Bond enthalpy in } \mathrm{Cl}_{2} & +243 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \text { Electron affinity of } \mathrm{Cl} & -349 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \text { Lattice enthalpy of } \mathrm{NaCl} & +790 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{array}

Question (b)

(b)

Consider the lattice enthalpies of MgF2,MgCl2\mathrm{MgF}_{2}, \mathrm{MgCl}_{2} and CaCl2\mathrm{CaCl}_{2}. List these from the most endothermic to the least endothermic and explain your order.
Most endothermic
Least endothermic

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