Chemistry 31 Tentative Laboratory Schedule Spring 2012

 

 

Experiment

 

Due Date

 

Grading

Approximate Tolerances

Calibration of Buret and Pipet

February 13

2 points based on precision

0.0250mL

Chloride Lab

March 5

13 pts (11 for accuracy, 2 for precision)

0.30%, 0.25%

Water Hardness Lab

March 14

10 pts (8 for accuracy, 2 for precision)

0.55%, 6ppm

Atomic Absorption Spectroscopy

April 9

10 pts (10 for accuracy)

5%

Soda Ash Lab

April 16

10 pts (8 for accuracy, 2 for precision)

0.5%, 0.1%

Spectrophotometric Analysis

April 25

10 pts (all for accuracy)

2.5% each

Formal Water Report

April 30

10 pts

--

Ion Chromatography

May 7

10 pts (all for accuracy)

2.5%

GC

May 9

10 pts (all for accuracy)

2.5%

1. Lab reports are due at the beginning of lecture and must be turned in by the due date to receive full credit. If laboratory reports are not completed or are not in a correct format, they will be returned once without grading to be completed and put in the correct format. Tentative report due dates given above are roughly one week past the last day expected for work on the experiment and may be changed if the class as a whole is behind schedule. The penalty for late lab experiments is 2 points off for each week late. Lab reports turned in after May 9 (including recalculations/resubmissions) normally receive zero credit. Also, note that some of the calculations required in the reports are difficult and require the use of a computer. It is a good idea to try to do the calculations a few days (or more) before the deadline. Lab reports that are emailed to the instructor will not be accepted for any reason.

2. Experiments with poor scores can be 1) recalculated and resubmitted one time if it appears likely the poor score was the result of an incorrect calculation or 2) redone. You are allowed to redo one experiment in the lab at the end of the semester if time allows. No penalty will be given for resubmitted experiments as long as they are resubmitted within one week of being returned to the student. You are allowed to refill/replace an unknown once during the semester without penalty. Additional refills or replacements will cost 2 lab report points.

3. Grading for accuracy will be based on the percent error calculated between the reported value and the true value. A full accuracy score will be received if the percent error is less than a tolerance value (ranging from 0.3% to 5% depending on the experiment). Larger percent errors will result in a loss of points. For example, if an experiment has a 0.4% tolerance and a student's percent error is 1.0% that student would receive an 8.5 or a loss of 1.5 points for being 0.6% past (1.5 times) the tolerance. Very large percentage errors will result in receiving no fewer than 40% of the possible points.

4. Grading for precision will be based on reported uncertainty limits compared to expected uncertainties.

5. The Atomic Adsorption Spectroscopy Lab requires a formal laboratory report. The purpose of this assignment is for you to practice your technical writing skills, and to think about how you may communicate scientific results clearly to others. Details concerning this report will be handed out separately.

 

6. Your laboratory notebook will be collected and graded at random times twice during lab periods. Your grade will be based on 1) correct formatting of the laboratory notebook, 2) completion of pre-lab calculations prior to conducting lab work, 3) evidence showing that all data was put directly into the lab notebook, and 4) a reasonable attempt to keep data organized so it is understandable. The lab instructor may deduct lab notebook points at any time if you are using something other than your laboratory notebook during lab to record data. See pages 11 and 12 of your lab manual for more information.