Experiment 16 (Part 2)

Hi everyone,

This would probably be my last post for this semester! It is nearly over :)

So this lab is quite a long one since they have to hand in their reports at the end of the lab again.

Here are the tips of the week:

  • Remind them to change their salt bridges when they get dry. Specially if they are getting weird numbers it sometimes helps
  • Double check that they are using the Cu and Pb electrodes not the other ones
  • Slope of the delta G vs. T is equal to negative delta S meaning that if they get a negative slope they should end up with a positive change in entropy
  • It would be helpful to demonstrate the use of the repipet
  • This lab doesn't result in very accurate data so don't get surprised if your students don't get numbers near to the literature
  • Only the electrode should be in the solution and not the alligator clip
  • Remind them about the 1022 review session on May 9th from 6 to 8 PM in Smith 100 
  • Next week is check out week. They all have to show up!

I would also like to take this opportunity to thank the Monday afternoon TAs who have helped me through this semester with their helpful tips: Roger, Adam, Evan and Nick. Thanks guys!

Have a good rest of the semester :)

 

 

Experiment 16 (Part 1)

Hi everyone,

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!

 

Experiment 15 (week 2)

Hi all,

This week's lab doesn't take long. Here are the important points:

  • Strongly emphasize that they have to write down the unknown numbers correctly.
  • Tell them that water can be an option for their unknowns.
  • It's better if they don't use their plastic pipettes since they might be contaminated. I told them to use the disposable glass pipettes and plastic bulbs which are located in the bins underneath the blackboards.
  • Remind them that next week is make up session.

That's all for now!

Have a good one :)

Experiment 15 (Part 1)

Hi everyone,

The duration of this week's lab depends on your students' technique. I hope the below points would help them and you save some time:

  • Ask them to use the well plate's lid. It would reduce the amount of waste and they can see the product of their mixture way easier.
  • Emphasis to split the work between two partners. I even had groups who split the work between 4 people (two groups).
  • Tell them to predict the reactions that wouldn't happen in advance, they can use Q1 as a good reference. This would save them a lot of time.
  • The waste goes into special containers and is not neutralized.

Have a good week!

Experiment 14 (week two)

Hi,

I hope you all had a refreshing spring break.

These are the points that come in mind for this week's experiment:

  • First of all, make sure the students are using table 3 to indentify their unknown acids. Some tend to use table 1
  • Emphasize that they should follow the directions in the manual to open logger pro:   C:\Program Files\Logger Pro 3\en-US\...
  • When they are calibrating their probes some get confused on what to type in the box that shows up. Tell them that they are supposed to type in the pH of the buffer solution and not the voltage reading. You can avoid this problem by properly explaining what calibration means!
  • Some of the students might have diprotic acids so tell them to be careful when they reach the first equivalence point (around 8-12 mL)
  • Some of the GoLinks have poor connections. Tell them to check for these poor links before starting, to avoid any re-titrations
  • Remind them to be careful with the sig figs on pH values
  • There are limited number of buffer solutions, so make sure your students return them back to their place once they're finished

Have a good week :)

Experiment 14 (week one)

Hello,

Lab 14 (week one) is a very long lab.

Here are the points that seem important:

  • KHP is an abbreviation for potassium hydrogen phthalate (KHC8H4O4). Lots of the students think they should add the molar mass of K, H and P to get to its molar mass !!! Make sure that doesn't happen.
  • Lots of students have problem with calculating the GEM. I think it's a good idea to walk around and take a good look on their calculations and make sure they are doing it correctly. In my section some of them were using "Table 1" to figure out the # equiv of NaOH. Watch out for that.
  • They have to keep their unknown and NaOH solution in their drawers for next week.
  • Make sure they cap the NaOH bottles beside the scales.
  • It's a good idea to show them an example of what we mean by pale pink. You can use one of the first students' solutions that turned out well, as an example.
  • They would need to use Table 3 to answer Q10.

That's all for now,

Have a good spring break :)

Experiment 13

Hi everyone,

Lab 13 is quite a long one. Be aware!

Some tips to help the lab run more smoothly:

 

  • This lab has a waste treatment that takes some good amount of time. Tell them to make as less waste as possible so they'll finish on time. For example, tell them to use the well plate's lid to carry out the reactions (then they'll make less waste in first place).
  • If you tell them to use the lid they might end up having less than 15 drops for titration.I don't think it's a big deal as long as they count how many drops they are using.
  • The lab manual tells them to wait for 10 minutes between washes. They don't have to wait that long. They can go to the next step as soon as the white precipitate has settled down. 
  • I think it's a good idea to emphasize the 1:6 ratio between iodate and thiosulfate in your talk.
  • When they are adding the KI crystals to the solution they should use scoopulas not their hands!!! Also tell them that it's OK if the number of crystals aren't exact.
  • Remind them to use filter papers in their funnels! and I also think it's a good idea to show them how you fold a filter paper correctly.

That's all for now,

Have a good week

Experiment 12

Hi everyone,

These are the points that seem important for this lab:

  • Make sure you highlight that this week when setting up LoggerPro they should use Appendix G - "Collecting a complete spectrum"
  • Remind them that in all runs they use 5 mL of Fe(NO3)3
  • Emphasize that in Keq we use the equilibrium and not the initial concentrations. It is a good idea to go through the equilibrium concentration calculations (ICE table) in your prelab talk or individually
  • Don't forget to put up the beer's law equation on the board which you would find from the stockroom
  • Make sure they are using Excel correctly to make their spread-sheets. Some of them either don't understand the point of using Excel and start calculating and typing numbers in themselves and some just don't know how to use Excel.
  • Tell them to be careful about contaminating the solutions in part 2
  • Don't forget to pick up your evaluation forms from Nancy's office

That's all,

have fun with all the snow :)

Experiment 11 (Part 2)

Hi all,

This experiment went pretty smooth and fast.

Things to have in mind:

- It seems like all laptops have Office '10 on them now. So the part in the lab manual that speaks about the "chart wizard" confuses some of the students. Tell them to not pay attention to it unless they have an older version of Office installed.

- Tell them to be very careful with units specially units on the rate constant, frequency factor and activation energy.

- Emphasize that in the Arrhenius equation T actually stands for temperature and not time . Lots of them make that mistake.

- It is helpful to put up the equations for the integrated rate laws.

- Make sure they have the number to their datasets written down. That's what you need to grade them!

 

Nothing more,

Enjoy the great weather this week :)

Experiment 11 (Part1)

Hi everyone,
I hope you all had a great weekend :)
This week's lab is quite long.
Things to have in mind with this experiment:


- In the lab manual it tells them to run each experiment for 10 minutes. This is too
  long. Tell them to run each for 2-3 minutes.
- Remind them to select the 415 nm wavelength and unselect the other wavelengths.
- Make sure that when they are plotting their data in Excel they have "log Q" on the
  y-axis and not the x-axis.
- Encourage them to do their Excel graphs or at least the calculations neccesary for it
  in the lab, while you're around. They would learn better and it would save you time
  when grading.
- Tell them to calibrate their spectrometers with water before starting the runs.
- In your prelab talk try not to confuse them with too many details about the calculations.
  Keep reminding them that the goal is to find x,y and z (orders of reactants). Sometimes
  they really get lost.
- Maybe a good idea is to remind them when the "M1V1 = M2V2" formula is used.

That's all for now,

Have a good one !