Chemistry 31 Laboratory Grading: Report and Quiz Schedule – Fall, 2014


Laboratory Experiment Report           Due Date     Grading           Tolerance#

1. Calibration of Buret/Pipet                     Sept. 22        2 pts                 N/A  (0.1)

2. Chloride Lab                                       Oct. 15         13 pts               0.3  (0.5)

3. Water Hardness Lab                           Oct. 27         10 pts               0.5  (1)

4. Atomic Absorption Spectroscopy        Nov. 17        10 pts               5 ea.

5. Soda Ash Lab                                     Nov. 26        10 pts               0.5  (0.5)

6. Ion Chromatography                            Dec. 3           10 pts               5

7. Formal Water Report                          Dec. 8           10 pts               N/A

8. Spectrophotometric Analysis                Dec. 11*       10 pts               2.5 ea. compound

9. GC                                                      Dec. 11*       10 pts               2.5

*It is recommended that you turn in these lab reports earlier in case you make any calculation errors.

#See notes 4 and 5 below for the meaning of the tolerance scale.



1.  Laboratory experiments must be turned in by the due date to receive full credit.  If laboratory reports are not completed or are in an incorrect format, they will be returned without grading.  Report due dates are roughly based on one week past the last day expected for in-lab work and may be postponed.  The penalty for late lab experiments is 2 points off for each week late.  Lab reports turned in after Dec. 11 (including recalculations/resubmissions) receive zero credit.  Also, some reports require calculations using a computer, so it is suggested that you try to do the calculations at least a few days before the deadline.

2.  Lab report formats:  Reports 1, 3, 5, 6 and 9 are submitted by filling out a copy of the report form at the back of the lab manual (similar looking computer-generated reports are acceptable).  Reports 2 and 8 require turning in a spreadsheet (see example spreadsheets in the lab manual).  For report 4, the report page, two spreadsheets and two plots (1 for each element) must be turned in.  The formal lab report (number 7) will be a 3 to 5 page written report of the analysis of the tap water sample in the atomic absorption spectroscopy and the ion chromatography labs.  This report will be graded based on the writing quality and content.  More details will be given later on the format required for this report.

3.  Grading will be based on precision (2 points each for labs 1, 2, 3, and 5) and accuracy (remainder of points for labs 2, 3, and 5 and all of the points in 4, 6, 8, and 9).

4. Grading for accuracy will be based on the percent error calculated from the reported value and the true value.  A full score will be received if the percent error is less than a tolerance value (1st value shown above).  Percent errors larger than the tolerance will result in loss of points.  For example, an experiment has a 0.5 % tolerance and a student's percent error is 1.2%, that student would receive a 8.6 or a loss of 1.4 points for being 0.7% past (1.4 times) the tolerance.  There will be a minimum accuracy score of 40% of the points for completed reports.

5.  Grading for precision will be based on reported uncertainty.  If your percent uncertainty is less than the value listed in parentheses under tolerance, you will receive full credit.

6.  If it appears likely a poor score was the result of an incorrect calculation or if the initially submitted lab report was incomplete (and returned without grading), the report may be corrected and resubmitted.  The new report must be attached to the originally submitted report, must be done within one week of return of the report, and can only be resubmitted once for each experiment.  You may not resubmit the formal lab report.

7.  If you receive a low score, you may repeat one experiment if time permits.  However, students are limited to only one "free" unknown request (subsequent unknown requests will be taken with a 2 point penalty).  No unknown request can be made the last week of the semester.

8.  Laboratory notebooks will be collected at random during the semester and graded for a total of 10 points.  It will be graded on 1) correct formatting (table of contents, page numbers, etc.), 2) inclusion of pre-lab calculations needed for current laboratory exercise, 3) a reasonable attempt to keep data organized, and 4) data entered correctly.

9.  The laboratory procedures quiz (5 pts) will be given on 9/11 and 9/15 and be focused on reading the first 16 pages of the lab manual, understanding how lab grading is done, and on following safety and procedural information given in the lab lectures during the first week.