August 2010 Archives

Expt 1

Experiment 1 Parts I and II

First, I would like to apologize to all of the Tuesday TAs, since as the Monday Forum TA I was supposed to have this done last night. It won't happen again.

Experiment 1, Parts I & II didn't seem to be conceptually difficult for the students. Since Monday had both check-in and the experiment to do, I gave an abbreviated pre-lab that discussed only how to use glassware/balances/conductivity probe, etc. This seemed to be helpful for them.

Some students struggled with the multiple dilutions in Part II, however I received fewer questions on this than in previous semesters.

Sometimes the computer will lose the connection to the conductivity probe. This causes the green collect button to become gray and not collect data when pressed. To fix this, have your students reopen the calibration file in Logger Pro (see paragraph 5 of Appendix F). Also check that there isn't a faulty connection in the USB/Go Link/Probe wiring.


Expt 1 Part III

Part III went much more smoothly than Parts I and II. All students completed everything for Part III, so time should not be an issue.

The biggest problem I had in my lab section was Q16. I would say 75% of my students had no clue where to start on this one. In my pre-lab talk I had briefly touched on precipitation reaction/titration/equivalence point, but it obviously didn't help. Almost all of the students also used M1V1=M2V2 for Q12, which is also incorrect. I ended up demonstrating how to do Q12 (without actually plugging numbers in) in order to teach them about Q16.

Lab equipment wasn't an issue. I showed each lab pair how to use a buret and explained how to find the total volume. Also remind them to use the volumetric to make the stock NaCl solution, a surprising number forgot about that in a week.


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