Chapter 12: Problem 71
Which of the following arrangements show the correct order of increasing lattice energy? (a) \(\mathrm{BaSO}_{4}<\mathrm{SrSO}_{4}<\mathrm{CaSO}_{4}<\mathrm{MgSO}_{4}\) (b) \(\mathrm{MgCO}_{3}<\mathrm{CaCO}_{3}<\mathrm{SrCO}_{3}<\mathrm{BaCO}_{3}\) (c) \(\mathrm{LiF}<\mathrm{LiCl}<\mathrm{LiBr}<\) Lil (d) \(\mathrm{NaF}<\mathrm{KF}<\mathrm{RbF}<\mathrm{CsF}\)
Short Answer
Step by step solution
Understanding Lattice Energy
Analyze Metal Sulfates (Option A)
Examine Carbonates (Option B)
Review Lithium Halides (Option C)
Evaluate Alkali Fluorides (Option D)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ionic Size
In terms of ordering, for ions like those present in lattice structures:
- Smaller ions generally lead to stronger lattice energy.
- Larger ions tend to decrease lattice energy due to increased distance between charges.
Ionic Charge
Consider these points:
- Lattice energy is directly proportional to the magnitude of the charge on the ions. Higher charges generally mean stronger attractions.
- Ions with +2 or -2 charges, for instance, will result in higher lattice energy than those with +1 or -1 because of increased force of attraction.
Crystal Lattice
Key features of a crystal lattice include:
- It represents a systematic, repeating pattern extending in all three spatial dimensions.
- This organization maximizes attractive forces while minimizing repulsion, enhancing stability.
Metal Sulfates
For these compounds:
- As you move from larger ions (Ba) to smaller ions (Mg), the lattice energy increases due to the decreased ionic size.
- This size difference influences how tightly the sulfate ions can pack, affecting the overall stability and energy of the lattice.
Carbonates
- The increasing size from Mg to Ba leads to a decrease in lattice energy.
- The larger the metal ion, the less tightly the carbonate ions are held together, reducing stability and lattice energy.
Lithium Halides
- When looking from LiI to LiF, the ionic size decreases, leading to stronger attractions between ions and increased lattice energy.
- LiF has the highest lattice energy because of the small ion sizes and resulting strong interactions.
Alkali Fluorides
Consider these points:
- NaF, being the smallest, has the highest lattice energy due to shorter ion-to-ion distances.
- As you progress to CsF, the lattice energy decreases owing to the reduced electrostatic interactions caused by larger ionic sizes.