Wednesday, July 1, 2015

Summer 2015: Lecture 10 Speciation

This lecture covers fundamentals of chemical kinetics thermodynamics, mainly as a review. Emphasis of the lectures is applied to information useful for speciation modeling. Equilibrium constants are discussed. The role of chemical activity is provided. Calculations and models for speciation are presented. Equilibrium modeling using EXCEL and the program CHESS are presented. Solubility calculations are provides, with examples for the uranium system.

14 comments:

  1. I'm having trouble following some of your work when you discuss solubility calculations. On slide 20 you find the Ksp for the dissociation of AgCl by taking (1E-5)^2 but the concentration of the silver ion in solution is only 1E-5 and the stoichiometric coefficient is 1.

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    1. Nevermind, I totally see my mistake... concentration of Ag and Cl are equal so it's (1E-5)*(1E-5)

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  2. I was a little confused by question 2 on the quiz. Would mind taking a look at my scratchwork and letting me know if I'm going about it the wrong way? If so I might check out the CHESS software.
    Thanks

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    1. Let me know what answers you got and what specifically is unclear. I did not see any work.

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  3. For the last question on the quiz, I had a bit of difficulty. Since the question is asking for a percent does that mean we just look for the concentration of the UO2OH+1 over the sum of the concentrations of UO2OH+1 and UO2+2?

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  4. That would be a percentage. Also just look at the equation. You are given the value for beta on page 8 of the lecture. For this specific case the equation is:

    beta=[UO2OH+]/([OH-][UO22+])
    I rearrange this to get
    beta [OH-] =[UO2OH+]/[UO22+]
    so I know a few things.

    pOH + pH = 14. You get pH in the question, now you know pOH, hence [OH-]

    so at any pH you can get the value for [UO2OH+]/[UO22+]

    you also know 1=[UO2OH+] + [UO22+]

    you now have everything you need to answer the question, you can also just select a concentration and solve.

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  5. The lecture's pH and solubility calculations brought me back to my Analytical chemistry days. Glad to revisit that!

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  6. At first I had the same issue as Gabe thanks for clearing it up!

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  7. I tried to look at the excel calculation sheets for this lecture from the website but they were unable to load on my computer.

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