The lattice energies of FeCl3, FeCl2, and Fe2 O3 are (in no particular order) -2631,-5359, and -

step 1 So in this video we're going to talk about question 68 from chapter 8, which tells us the lattic

The lattice energies of FeCl3, FeCl2, and Fe2 O3 are (in no...

The lattice energies of $\mathrm{FeCl}_{3}, \mathrm{FeCl}_{2},$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ are (in no particular order) $-2631,-5359,$ and $-14,774 \mathrm{kJ} / \mathrm{mol}$ . Match the appropriate formula to each lattice energy. Explain.

Key Concepts

Influence of Anion Charge and Size

In comparing different compounds, not only does the cation charge matter but so does the anion charge and its size. Anions with larger charges (or those that are smaller and can get closer to the cation) contribute to stronger ionic attractions. In the example context, an oxide ion (O2-) typically results in a higher lattice energy than a chloride ion (Cl-) when paired with comparable cations.

Lattice Energy

Lattice energy is the energy released when gaseous ions come together to form an ionic solid. It is an indicator of the strength of the ionic bonds in the solid and depends on both the magnitudes of the ionic charges and the distances between the ions (which are influenced by their radii).

Coulomb's Law in Ionic Solids

Coulomb's law tells us that the electrostatic force between ions is directly proportional to the product of their charges and inversely proportional to the distance between them. This means that compounds formed from ions with higher charges or with smaller ionic radii (leading to shorter internuclear distances) exhibit greater (more negative) lattice energies.

Ionic Charge Effects

The magnitude of ionic charges plays a key role in determining lattice energy. For example, compounds containing Fe3+ (a higher positive charge) will tend to have higher lattice energies than those containing Fe2+ when paired with similarly charged anions, because the product of the ionic charges, which drives the strength of the electrostatic attraction, is larger.

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