Category Archives: Announcements

General announcements. All students should read these.

CHM 110: Experiment 3B shared data (Wednesday)

Here’s the shared data from CHM 110 Experiment 3B. These are the ratios of mass product / mass barium chloride dihydrate that you need to complete the table on page 74 and answer the questions on pages 75 and 76.  This is data for the Wednesday lab section (section 2)!

Ratio of (mass product / mass BaCl2.2H2O):

  • 0.85100
  • 0.85194
  • 0.84900
  • 0.84466
  • 0.85160

The write-up for Experiment 3B is due at our next lab meeting. If you have any questions about either the calculations or the rest of the write-up, either come by my office or ask here in comments.

You may use your TI-83 caclulator or your spreadsheet to find the standard deviation – you don’t have to calculate it by hand.

The missing-text blues

A few people have told me that when they try to print the board notes, they’re having trouble with fonts disappearing.  I’ve reproduced the problem myself in one of the student conputer labs in the 5000 muilding.  I have discovered a workaround for the problem – use a different PDF viewer.  Here’s one that I tested in the school computer labs:  Sumatra PDF

If you’d like to use Sumatra PDF in one of the school labs, then download the Sumatra ZIP file to your desktop, and double-click it.  Copy the single file inside the folder that opens up to the desktop, then double-click it to run it.  You can also copy that file to a USB pen drive and take it with you to any other computer.

To view or print the notes for your class, just save them to your Desktop (right-click on the link), then open them with the Sumatra PDF viewer.

Any questions?  Ask here!

Melamine in the news

It looks like there’s trouble in China.  Supplies of milk powder meant for Chinese infants are tainted with melamine – the same chemical found in last year’s dog-food scare.

On Sept. 17, China’s minister of health, Chen Zhu, announced that three babies had died, more than 150 were suffering from acute kidney failure, and an additional 6,000 infants had become sick after drinking milk made from milk powder tainted with melamine.

Now you might be wondering why on earth a company would add melamine to powdered milk.  Could it have been accidental?  Or was there some reason to add this compound?

Consider this:  The amount of protein in foods is often determined based on total nitrogen content.  That’s because proteins contain a fairly regular amount of nitrogen – about 16% by mass.  Take the total nitrogen content, multiply by a conversion factor, and you have a good estimate of protein content of the food.

Take a look at melamine.

Melamine, C<sub>3</sub>H<sub>6</sub>N<sub>6</sub>. Nitrogen atoms are indicated in blue.

Melamine, C3H6N6. Nitrogen atoms are indicated in blue.

Simple assay methods for total nitrogen content can’t distinguish the nitrogen in melamine – which is about 67% nitrogen by mass – from the nitrogen in proteins.

The tested substance appears to have a higher protein content than it actually does – since analysts assume that almost all the measured nitrogen comes from actual protein.  This is a reasonable assumption for uncontaminated materials, but is open to abuse by the amoral.

Software update

This morning, I updated the WordPress software that powers this site.  If the update went well, you won’t notice any differences in using the site (it was a minor bug-fix update).

If you notice any problems with the site like broken links or buttons not doing what they’re supposed to, please let me know.

CHM 100 Test 1

I’ll be posting the problem solutions from Test #1 on the web site either this evening or tomorrow.

If you missed test 1:

  • Your final exam grade will count in place of the missed test, in addition to the 20% the final already counts.

If you did not miss test 1, and miss no other tests:

  • Your final exam grade will replace your lowest test grade, in addition to the 20% the final already counts.
  • If your final exam is your lowest test grade, then it will count 20% (as specified in the syllabus, but will not replace a test grade.

Oops! Correction to CHM 100 syllabus

CHM 100 students!  The class/lab times in the syllabus passed out on Monday were incorrect.  The correct times are:

Time Room
Lecture (both sections) 9:05 AM – 9:55 AM, MWF 5401
Lab, Section 1 11:15 AM – 2:05 PM, T 5402
Lab, Section 2 11:15 AM – 2:05 PM, TH 5402

The [online syllabus] has been corrected.

Remember that we won’t be meeting for laboratory this week, but lecture will meet as scheduled. Make sure to buy your laboratory manual before next week!

Grades Posted!

I have posted final grades for CHM 100 and CHM 111. To get your grade, log on to the WebAdvisor system. If you have any questions about your grade or if you wish to view your final (you don’t get to keep a copy of the final, sorry!), you may come by the office sometime after August 11th. Please don’t call to ask about your grades, because I’m not allowed to discuss confidential information like grades over the telephone!

[Happy Turtles]

It's turtles all the way down!

I hope you enjoyed chemistry this term, and I hope you now have some time to relax and enjoy what’s left of the summer – just like these turtles!

Note:  Your grades have been entered into the system.  It’s possible that they may not show up before Monday.  So if you check over the weekend and the grades don’t seem to be there, don’t panic.