Solids
Ch 7: 233-236; 247-252
Goals: Predict lattice energy and solubility using ion size, HSAB, and packing; (Try for Wed: relate silicate structure to stoichiometry)
HW: Ch 7, # 15, 17, 19, 20, 28
Slides: SLides_Sept_26b
3 thoughts on “9. Sept 26”
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Could you please post the answer key for chapter 7 before class on Wednesday? I think I am confused about some of the signs in calculating the lattice energies, but just looking at the solutions might clear up my confusion.
Hi,
The Ch7 answers are on the post for Sept 23.
The signs for lattice energies ARE confusing, because there are two (opposite) conventions used by about 50% of chemists. Your textbook uses the convention in which DeltaH corresponds to lattice formation from the gaseous ions (eg: Na+(g) + Cl-(g) -> NaCl (s)). Therefore lattice energy is negative in Miessler and Tarr.
In lecture, I used a diagram from a competing textbook with the opposite convention (breaking the lattice into gaseous ions). My mistake, and I’m sorry.
I promise that I will clearly state the reaction in question when asking you about lattice energies, so that you can rely on your chemical intuition to know whether DeltaH will be negative or positive.