Exam code: YCH11
The table shows the theoretical and experimental (Born-Haber) lattice energy data for two metal halide compounds, sodium chloride and magnesium iodide.
| Lattice energy / kJ mol–1 | |
Metal halide | Theoretical | Experimental (Born-Haber) |
Sodium chloride | −770 | −780 |
Magnesium iodide | −1944 | −2327 |
Using the data, compare and contrast the type and strength of bonding in these compounds. Give reasons for your answers.
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This question is about the energetics of ionic compounds.
Define the term lattice energy. Include a balanced equation, with state symbols, to represent the lattice energy of magnesium iodide, MgI2.
The Born-Haber cycle for MgI2 is partially drawn below.
Complete the Born-Haber cycle for MgI2. Your diagram must include:
The correct species at each energy level, with state symbols
All electrons shown explicitly
Labels for each enthalpy change
Using the data below and your Born-Haber cycle, calculate the lattice energy of MgI2.
Enthalpy change | Value / kJ mol−1 |
|---|---|
ΔfH°(MgI2) | −364 |
ΔatH°(Mg) | +148 |
ΔatH°(I) | +107 |
1st IE(Mg) | +738 |
2nd IE(Mg) | +1451 |
1st EA(I) | −295 |
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