I hope you had a good weekend.
This lab was quite a long one. Here are the tips that might help you:
- Reminder: This week they hand in their reports at the end of the lab (that's why it takes longer than usual)
- They have to make an agar gel and wait for it to cool down. A good way for saving time is to tell them to get started right away and then give the prelab talk while they're waiting for the gel to solidify
- Walk around and make sure they have figured out the electrodes correctly. There is a very helpful chart beside every board that can be used:
Cu: orangish color, Zn: has a punched hole on it, Ag: not as flexible as Cd and Pb, Pb: flexible and soft (you can scratch it with your nail), Cd: also flexible and soft but not as much as Pb
- If they read zero while measuring a cell tell them to reverse the clips
- Some electrodes develop a black precipitate while reacting. Tell them to sand it off before every measurement if such a thing happens between runs.
- Make sure they are doing the second part correctly (determining the Ksp). It is a bit confusing for them. It doesn't hurt to put a scheme on the board of how one would set up the experiment. Also tell them that in this part they should use the same electrode for both half-calls, same as the cation (for example, measuring AgCl one uses Ag electrodes)
That's all for this week!