March 2011 Archives

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)


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)


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 :)

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