Today in lecture I went over all the course requirements in the syllabus. I know it may seem like a ton of information all at once, but please be assured that the TA's and I will work with you this quarter and if you ever need anything be sure to ask. Be sure to read over the syllabus and take the COAM quiz on Carmen.
I will try my best to keep this blog updated after every lecture and I will post the materials you will be responsible for on the quizzes and exams on here as well. As always I would appreciate any comments or suggestions as to how to make this resource more valuable to you as a student.
After all the logistical material was covered today in lecture I started on our first "unit," which is SOLUBILITY. Solubility was first introduced to us back in Chapter 4 of the textbook and we were only given a chart of "solubility guidelines" telling us if an ionic substance is "soluble" or "insoluble" in aqueous solution. This table is a way to represent solubility in a qualitative sense, but in this course we will look at solubility in a quantitative sense, or we will determine the exact amount of a substance that dissolves.
To determine just how much solute will dissolve in an aqueous solution, chemists can analyze the equilibrium constant, or Ksp. The Ksp is a measure of how much of a solid dissolves to form a saturated solution.
Typically Ksp tables are generated for various inorganic compounds. The chart listed here is shown in the appendix of the lab manual. There is a relationship between these two tables. Focus a minute on the chlorides in the solubility rules table. All chlorides are soluble with the exception of Ag+, Pb2+, and Hg22+. These are all insoluble, or will form precipitates. All other chlorides will remain in solution. This can now be used as an effective separation technique if we want to isolate Ag+, Pb2+, and Hg22+ from any other cations. This is exactly the case for Ex.p #25 Group I in the qualitative analysis. If you look at the following figure you can now start to see the relationship between these two tables. If a compound is "insoluble," or more accurately, "slightly soluble" there will be a Ksp value associated with it. The smaller the value for the Ksp, the less soluble a substance is. Let me reiterate that the The Ksp is a measure of how much of a solid dissolves to form a saturated solution.
Now lets go back to the Exp. #25 Group I analysis. At the beginning of Lab #2 you will be handed an unknown compound that will consist of one of the three scenarios:
1. Ag+ only
2. Pb2+ only
3. Both Ag+ and Pb2+
What I want you to do is look at the flowchart on the back of the pre-lab or in the lab manual and think of what observations would lead to the confirmation or presence of Ag+, Pb2+, or both. Be sure to have this determined before you come into lab and Group I will not take you very long at all to complete.
Also, keep in mind that Exp. #25 I, II, and III is a long continuation. As soon as you complete Group I you should start right away with Group II. There is a deadline to identify the cations in each of the unknowns for these labs so you do not want to waste any time and the more prepared you are before you step into the lab, the faster the analysis will go.
You should also be starting with Exp. #25 on Lab #2. If you do not finish Lab #24 leave that till the end of the quarter. I will make an announcement in class on Wed. about this as well.
We will discuss how to relate molar solubility to the Ksp and to also calculate how many grams of a substance that will dissolve in a L of soln. We will then look at factors influencing solubility and come up with ways to manipulate the solubility or get something to dissolve that would seemingly be insoluble.
I hope everyone had a great first day of classes and if you need anything from me please let me know. Thanks, Dr. Fus
Songs Before Class:
Bruce Springsteen: Glory Days
Mase: Welcome Back
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