TOJC misc
carol krancich (carolkrancich@msn.com)
Wed, 25 Sep 96 04:57:00 UT
Justin and Angie, regarding the lab. I think the reference contains all of the
analgesics we tested in this lab (acetaminophen, aspirin, etc.). Justin, for
the Rf, you're just measuring how far the "dot" of the unknown chemical moves
in comparison to the known samples and the solvent. Measure how far the "line"
of the solvent is from the bottom edge of the TLC sheet; then measure how far
the "dot" of unknown chemical moved. The Rf is the ratio of the two ("dot"
distance/"line" distance). It doesn't matter what units you use, since you're
looking at the ratio, but the lab instructor today suggested millimeters.
Then you can compare that to the known samples to determine what was in your
unknown. I know, it's clear as mud, right?
Aaron, for problem 3.4, Ka = [product][product]/[reactant]. Remember that
the brackets indicates concentration in molarity. So for this problem, the
reactant is HCO2H, and the products are HCO2- and H30+. You are given the
concentration of formate ions, and the Ka, so just plug those numbers into the
formula and "solve for X."
Ka= 1.78 x 10-4 = [HCO2][H3O]/ [0.1]
So multiply 1.78 x 10-4 by 0.1; the root of that is your concentration of
formate ions and hydronium ions.
Somebody help me out here if I've made an error. C.E.K.