I started lecture with some helpful hints to complete Lab #25 II. We discussed some overall chemical principles in the separations used in Exp #25 II and I pointed out from pg 51 of the lab manual that "The ability to control the [H+] (or the pH) of the precipitating ion makes selective precipitation possible." This statement is key in separating Group II and III.
The Group II ions will precipitate out as sulfides in acidic solution, while the Group III sulfides will remain as ions in acidic solution.
Manipulation of the pH allows us to precipitate out the various other group III ions and we did some calculations to determine the pH each ion will begin to precipitate.
I ended class by listing the factors influencing solubility that we will cover in great detail in the next two lectures. They are: Common Ion, pH, Complex Ion, and Amphoterism (Section 17.5).
Homework: Solubility Set #1-15, 17, 20-22, 24-28; Exp #25 Homework set #1-10
Reminder: Quiz this week in Wed or Thurs during the first 20 min of lab
Congrats to the North Carolina Tarheels. Enjoy your one shining moment. It was a great tournament this year, but nothing can beat this moment from 2007.
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