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lattice enthalpy born haber
A LevelChemistry~4 min read
Overview
This lesson delves into the concept of lattice enthalpy, a crucial measure of ionic bond strength. We will explore how Born-Haber cycles are constructed and used to indirectly determine lattice enthalpy, applying Hess's Law to a series of enthalpy changes.
Introduction to Lattice Enthalpy
Lattice enthalpy (ΔH_latt) is a fundamental thermodynamic quantity that quantifies the strength of ionic bonds within a crystal lattice. It is defined as **the enthalpy change when one mole of an ionic compound is formed from its gaseous ions under standard conditions**. This process is highly exoth...
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Key Concepts
- Lattice Enthalpy (ΔH_latt): The enthalpy change when one mole of an ionic compound is formed from its gaseous ions under standard conditions.
- Born-Haber Cycle: An indirect method for calculating lattice enthalpy using Hess's Law, by relating it to other measurable enthalpy changes.
- Enthalpy of Atomisation (ΔH_at): The enthalpy change when one mole of gaseous atoms is formed from an element in its standard state.
- First Ionisation Energy (IE1): The enthalpy change when one mole of gaseous atoms loses one mole of electrons to form one mole of gaseous +1 ions.
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Exam Tips
- →**Draw the Cycle Clearly:** Always draw a clear, labelled Born-Haber cycle in your exam. Use arrows to indicate the direction of each enthalpy change and ensure all species and their states are correct.
- →**Apply Hess's Law Correctly:** Remember that the sum of enthalpy changes in one direction around the cycle equals the sum in the opposite direction. Be careful with signs, especially for electron affinity (often negative) and lattice enthalpy (always negative).
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